Interactive system to study Assembly Language, Computer Architecture and Reverse Engineering. Microprocessor emulator with integrated assembler. Online reference, examples and tutorials .....(free).....

BeOS R5 Personal Edition for Windows comes in a self-installing executable, making installation easy and painless. If you're running Windows Millenium Edition, Windows NT, Windows 2000, or Windows XP, you will need to create a boot disk with the included utilities. Otherwise, you can simply double-click the icon installed on your desktop to launch the Be Operating System. This does not in any way alter or harm your Windows installation. BeOS Personal Edition is entirely self-contained within a file installed onto your Windows partition. If you would like to put it in its own partition, however, you may do that from within BeOS.....(free).....

BootPart is an easy tool for adding one partition in the Windows NT multi boot menu (for example, an OS/2 boot manager or Linux partition). Your active partition on your first hard disk must be a FAT16 primary partition. This can be a small partition. Bootpart 2.20 is compatible with Windows NT, Windows 2000 and Windows XP.....(free).....

The CBT tape is a collection of freeware for the IBM mainframe MVS and OS/390 operating system environment.....(free).....

For tweaking the new Windows Vista bootloader. With EasyBCD, almost anything is possible. Setting up and configuring Windows boot entries is simple, and there is no easier way to quickly boot right into Linux, Mac OS X, or BSD straight from the Windows Vista bootloader - on the fly, no expert knowledge needed......(free).....

The Extremely Reliable Operating System--EROS is a new operating system being implemented at the University of Pennsylvania. The system merges some very old ideas in operating systems with some newer ideas about performance and resource management. The result is a small, secure, real-time operating system that provides orthogonal persistence.....(free).....

FC64 is a low level Commodore C64 emulator written in AS3 and licensed under the GPL .....(free).....

The goal of the FreeDOS Project is to create a free implementation of MS-DOS. DOS is a popular system, and there is plenty of hardware out there that supports DOS. The FreeDOS Project was founded in 1994 by Jim Hall. FreeDOS is not a derivation of MS-DOS - we are not using or referring to any Microsoft code. We are instead using the description of the MS-DOS program as given in publications (such as the user manual) to create a program of our own that follows that spec.....(free).....

GAG (initials, in spanish, of Graphical Boot Manager) is a Boot Manager program. It's loaded when the computer is turned on and allows you to choose the operating system you want to use. Its main features are: Allows boot of up to 9 different operating systems. It can boot operating systems installed in primary and extended partitions on any available hard disk. Can be installed from nearly all operating systems. GAG doesn't need its own partition. It installs itself in the first track of the hard disk, wich is reserved for these kinds of programs. It can also be installed on a floppy disk, without using the hard disk. .....(free).....

GAG (initials, in spanish, of Graphical Boot Manager) is a Boot Manager program. It's loaded when the computer is turned on and allows you to choose the operating system you want to use. Allows boot of up to 9 different operating systems.....(free).....

Install Leopard on a PC. No Mac necessary......(free).....

Use your mouse to drag the lists up and down, then try to flick them like you're supposed to on the iPhone. The back button on the phone is also enabled .....(free).....

Mac OS and Windows can work together in harmony on the same home network, sharing files and printers, mounting one another's drives and using the same equipment, like wireless routers and USB drives. If you're considering a mixed Mac/PC home or office, here's a primer on how the two systems inter-operate (and the few instances when they don't.) .....(free).....

MIR-OS is a 32-bit multi-tasking Operating System for the i386+ developed completely from scratch by a group of Indian programmers. Some of the OS's features include full software multi-tasking, Memory Management (slab allocator), Modularized kernel (ELF module support), Semaphores, FAT12 filesystem, VESA graphics and many other features.....(free).....

An OS designed for teaching operating systems courses. The Nachos distribution comes with: an overview paper, simple baseline code for a working operating system, a simulator for a generic personal computer/workstation, sample assignments, a C++ primer (Nachos is written in an easy-to-learn subset of C++, and the primer helps teach C programmers our subset).....(free).....

NewOS is a free operating system with full source code available, along with periodic binary snapshots. Currently runs on Intel and AMD single and multiprocessor desktops, Sega Dreamcast. NewOS exists to explore some aspects of modern OS design, and to have fun in the process. According to the developer, "I seemed to have collected a bunch of old non-x86 machines that need something running on them. I figure, 'Hey, why dont I just port my OS over?' The rest is history" .....(free).....

The logic of Unix's design choice stands out more clearly when we contrast it with other operating systems. A design overview.....(free).....

Emulate PowerPC on an x86 machine. If you're brave and have the time, run OS X under Windows. PearPC is an architecture-independent PowerPC platform emulator capable of running most PowerPC operating systems. The following operating systems were tested and run (to some extent) in PearPC (ie. as clients): Mac OS X 10.3: Runs well with some caveats. Mandrake Linux 9.1 for PPC installer: Runs well. Mandrake Linux 9.1 for PPC after installation: Hard to boot. Runs very well afterwards. Darwin for PPC: Runs well. OpenBSD for PPC: Crashes while booting (accesses PCI in an unsupported way). NetBSD for PPC: Crashes while booting. AIX for PPC: Some people ask about that.....(free).....

PETROS? is a new 32 bit operating system for the 486+ family of machines. It is designed to be compatible with MS-DOS and Windows 95. PETROS? understands FAT12, FAT16 and FAT32 file systems with the Windows 95 long name extensions. The executable file format is a 32 bit file format closely resembling that of Win32 programs. It is intended to maintain full compatibility with win32 programs, and also to support native Java programs.....(shareware, $50 after trial).....

QEMU is a FAST! processor emulator using dynamic translation to achieve good emulation speed. QEMU has two operating modes: Full system emulation. In this mode, QEMU emulates a full system (for example a PC), including a processor and various peripherials. It can be used to launch different Operating Systems without rebooting the PC or to debug system code. User mode emulation (Linux host only). In this mode, QEMU can launch Linux processes compiled for one CPU on another CPU. It can be used to launch the Wine Windows API emulator or to ease cross-compilation and cross-debugging. As QEMU requires no host kernel patches to run, it is very safe and easy to use.....(free).....

Restart is a system utility for advanced users with more than one operating system installed on their machine. The program installs an icon in the notification area, and with a single click the computer will shutdown and restart with the selected operating system.....(free).....

According to the author, "ScaraOS is a 32bit mutiboot OS kernel for IA32 (PC/AT) systems. I wrote it to teach myself OS fundamentals and just to have a bit of fun. It already has PCI support, the beginnings of a paged memory management system, and the start of a VFS layer. It supports the basic PC/AT stuff such as timer, PIC, keyboard, floppy".....(free).....

Encompasses not only Mac OS X and its relevant ancestors, but the various operating systems that Apple has dabbled with since the company's inception, and many systems that were direct or indirect sources of inspiration.....(free).....

Emulators and all the TRS-80 software you can download .....(free).....

A completely new approach to an embeddable, scalable and distributable multitasking operating system. ?nOS has been developed from scratch and is not related to any other existing operating system. It is based on the SPHERE real-time microkernel, whose innovative architecture is the solid basis for the operating system. .....(free).....

VICE is a program that runs on Unix, Windows, OS X and many other machines and executes programs intended for the old 8-bit computers. The current version emulates the C64, the C128, the VIC20, almost all PET models, the PLUS4 and the CBM-II (aka C610). .....(free).....

VirtualBox is a general-purpose full virtualizer for x86 hardware. Targeted at server, desktop and embedded use, it is now the only professional-quality virtualization solution that is also Open Source Software. Some of the features of VirtualBox are: Modularity. VirtualBox has an extremely modular design with well-defined internal programming interfaces and a client/server design. This makes it easy to control it from several interfaces at once: for example, you can start a virtual machine in a typical virtual machine GUI and then control that machine from the command line, or possibly remotely. VirtualBox also comes with a full Software Development Kit: even though it is Open Source Software, you don't have to hack the source to write a new interface for VirtualBox. Virtual machine descriptions in XML. The configuration settings of virtual machines are stored entirely in XML and are independent of the local machines. Virtual machine definitions can therefore easily be ported to other computers. Guest Additions for Windows and Linux. VirtualBox has special software that can be installed inside Windows and Linux virtual machines to improve performance and make integration much more seamless. Among the features provided by these Guest Additions are mouse pointer integration and arbitrary screen solutions (e.g. by resizing the guest window). Shared folders. Like many other virtualization solutions, for easy data exchange between hosts and guests, VirtualBox allows for declaring certain host directories as "shared folders", which can then be accessed from within virtual machines .....(free).....

There are many web operating systems hoping to bring all your usual desktop applications online in one place. Some replicate the entire desktop, while others are startpages with info from around the web.....(free).....

Windows port of the UAE Amiga emulator.....(free).....

We don't know what this is, but we thought you might be interested since you can boot into it. According to the authors, "The ZigZag system is very hard to explain, especially since it resembles nothing else in the computer field that we know of, except perhaps a spreadsheet cut into strips and glued into loops. It is a PRINCIPLED SYSTEM OF INTERCONNECTION. Lists and Spreadsheets are rational ways of connecting things, but they have shortcomings. Hierarchical directories are a standard way of connecting things, but they have extreme shortcomings. The ZigZag structure (we don't know the best term-- zzstructure, zzspace, quantum hyperspace?) is extremely simple but has remarkable properties. It can be built into almost anything, and has default visualizations".....(free).....

Search as you type in various places in windows. "Listary is an excellent find-as-you-type search utility that makes searching items in large unmanageable lists of Windows applications a breeze. Items in Windows Explorer, Task Manager, Registry Editor, Windows Desktop, file Open/Save dialogs and numerous other components and third-party applications can be found instantaneously with this free utility that allows you to type any part of the item name to be searched."

Keep track of your notes (Thx Gerry). "Tomboy is a desktop note-taking application for Linux, Unix, Windows, and Mac OS X. Simple and easy to use, but with potential to help you organize the ideas and information you deal with every day."

A simple countdown timer. "All the timers I tested were too complex for my taste. I decided to write one that was dead simple, so you could run it, type in a time and hit enter. The aim of SnapTimer is to get out of the way and help you be productive. It's fast, lightweight and simple to use, but powerful too."

Easiest way to create junctions that I've seen. "Hardlinks provide the ability to keep a single copy of a file yet have it appear in multiple folders (directories). They can be created with the POSIX command ln included in the Windows Resource Kit or the fsutil command utility included in Windows XP. Thus, using standard Windows facilities Hardlinks can only be created at the command prompt, which can be tedious, especially when Hardlinks to multiple files are required or when one only makes occasional use of Hardlinks. Support for Junctions in standard Microsoft software offerings is even more limited than that offered for Hardlinks."

Linux style cmd.exe replacement which emulates the terminal. "Cygwin is a Linux-like environment for Windows. It consists of two parts: (1) A DLL (cygwin1.dll) which acts as a Linux API emulation layer providing substantial Linux API functionality. (2) A collection of tools which provide Linux look and feel."

One of the best freeware CD burners out there (IMHO). "CDBurnerXP is a free application to burn CDs and DVDs, including Blu-Ray and HD-DVDs. It also includes the feature to burn and create ISOs, as well as a multilanguage interface. Everyone, even companies, can use it for free. It does not include adware or similar malicious components."

A cmd.exe alternative with features you would expect from a modern program. "Console is a Windows console window enhancement. Console features include: multiple tabs, text editor-like text selection, different background types, alpha and color-key transparency, configurable font, different window styles"

Tips for the DosBox; some well known, some not. "Post Windows 2000 and Windows XP, the use of the Windows Command prompt has been on the decline. Everything that is done on Windows today is done through the graphical user interface. There are still some tasks that are done through the Command prompt, but we aren’t going to discuss about commands available for the Command line. There are plenty of references for that. Rather, we are going to find out those tricks that make working on the prompt easier."

AutoHotKey script to fix a really annoying thing about the old DosBox. "If you hop between the regular applications and the command prompt with any frequency the lack of CTRL+V paste is frustrating. Tweak the Windows command prompt to support keyboard-based pasting with a simple AutoHotkey script."

Print to PDF. "PDFCreator is a free tool to create PDF files from nearly any Windows application."

An alternative to the windows file finder that can also find duplicate files. "SearchMyFiles is an alternative to the standard "Search For Files And Folders" module of Windows. It allows you to easily search files in your system by wildcard, by last modified/created/last accessed time, by file attributes, by file content (text or binary search), and by the file size."

A program to rescue data from a damaged disk. "CD Recovery Toolbox (download, mirror) tool was developed for recovering damaged files from different disk types: CD, DVD,HD DVD, Blu-Ray, etc. You can use it to restore information lost as a result of some mechanical damage of the disk (scratches, chips, different spots on thesurface) or as a result of incorrect recording."

See what icons are in a file from its properties. "IconViewer is a free Windows Explorer extension that lets you easily view, copy, and save icons contained within programs and libraries. Open a file's Properties box, select the "Icons" tab, and view the icons contained in the file."

How to run the SFC when offline. "The System File Checker (sfc.exe) is an useful tool that lets you scan the integrity of Windows system files, and repair corrupt or missing system files. Numerous cases have been resolved thus far by running Sfc.exe with the "scannow" parameter. However, there are situations where in a corrupt or missing system file prevents Windows from booting normally, and running Sfc.exe from Windows isn’t possible. In such cases, Sfc.exe can be run offline using two additional parameters, via the Windows Recovery Environment (Windows RE) in Windows 7 and Windows Vista."

An alternative to the default device manager in windows. "DevManView is an alternative to the standard Device Manager of Windows, which displays all devices and their properties in flat table, instead of tree viewer. In addition to displaying the devices of your local computer, DevManView also allows you view the devices list of another computer on your network, as long as you have administrator access rights to this computer."

iReboot sits in your taskbar at startup, only taking up 400KB of memory, and lets you choose which operating system you want to reboot into. Instead of pressing restart, waiting for Windows to shut down, waiting for your BIOS to post, then selecting the operating system you want to boot into (within the bootloader time-limit!); you just select that entry from iReboot and let it do the rest. Thanks to Lifehacker

Online iPad simulator shows you how your web site looks and plays on the iPad

Kolibri is a small x86 assembler hobby operating system. It forked off MenuetOS in 2004 and has mostly been developed by ex-USSR community since. API and ABI is being enreached with developer-frendly features. User interface is not that good yet but we are trying to improve it as well. Your feedback is very appreciated, although help would always be much more valuable. Current 0.7.7.0 release introduces several kernel, applications and libraries updates Thanks to instant fundas

Google Android, the telephone operating system, has been ported to run on x86 machines, just like the one in front of you. ISO images are available. Unclear whether source code only is available. If so, you'll have to compile it yourself

Interesting experimental OS, maybe like a really souped up Commodore 64. x86_64, preemptive multitasking, multicore, open source, public domain. Live CD image so you can test drive or install.

Chromium OS is an open-source project that aims to build an operating system that provides a fast, simple, and more secure computing experience for people who spend most of their time on the web. Here you can review the project's design docs, obtain the source code, and contribute.

The only open source hypervisor, now available as a live CD

Test your Web site to see if it is ready for mobile customers

iReboot sits in your taskbar at startup (only taking up 400KB of memory!) and lets you choose which operating system you want to reboot into. Instead of pressing restart, waiting for Windows to shut down, waiting for your BIOS to post, then selecting the operating system you want to boot into (within the bootloader time-limit!); you just select that entry from iReboot and let it do the rest Thanks to gHacks

Online Virtual Windows Operating System. Windows4all.com is a Silverlight based online virtual operating system. It is is a website that simulates an operating system inside your web browser. Windows4all.com replicates the desktop environment of a modern operating system. You can launch applications right away without installation. Windows4all.com is web-based and requires Silverlight 3 to operate. Application runs in Silverlight’s security sandbox. By default code is restricted from accessing user's file system or doing anything that could hurt user's machine. Besides desktop, taskbar, start menu and sidebar, currently it includes such applications as File Explorer, Internet Explorer, Video Player, Rich test editor, RSS reader, Notepad, Paint and more. Thanks to Web Talk

Neatx is an Open Source NX server, similar to the commercial NX server from NoMachine

Run the Google mobile operating system on your PC using LiveAndroid, a LiveCD for Android running on x86 platforms. Want to give Google Android a try, but don't feel like buying a T-Mobile G1? LiveAndroid lets you download a LiveCD disc image of the Google Android operating system. Just burn the image to a disc, stick it in a CD-ROM drive, and reboot your computer and you can check out Android without installing it or affecting any files on your PC. This will not affect the operation of your current OS since it's run from a cd. You can also use the disc image in a virtualization application like VirtualBox, VMWare or Microsoft Virtual PC if you want to try the operating system without even rebooting your computer

Windows4all.com is a Silverlight based online virtual operating system. It is is a website that simulates an operating system inside your web browser. Thanks to instant fundas

The liveusb-creator is a cross-platform tool for easily installing live operating systems on to USB flash drives. Features Works in Windows and Linux! Completely non-destructive install. There is no need to deal with formatting or partitioning your USB key. Supports automatically downloading various Fedora releases, as well as Sugar on a Stick! Automatically detects all of your removable devices. Persistent storage creation. This lets you to allocate extra space on your USB stick, allowing you to save files and make modifications to your live operating system that will persist after you reboot. This essentially lets you carry your own personalized Fedora with you at all times. SHA1 checksum verification of known releases, to ensure that you've downloaded the correct bits

eyeOS is an Open Source Platform designed to hold a wide variety of Web Applications. eyeOS was thought of as a new definition of an Operating System, where everything inside it can be accessed from everywhere inside a Network. All you need to do is login into your eyeOS server with a normal Internet Browser, and you have access to your personal desktop, with your applications, documents, music, movies... just like you left it. eyeOS is the Cloud Computing Operating System. Work online -personally or collaboratively- with your files, office, calendar, contacts and much more. Your data is safe and always available. If you do not want to install eyeOS in your own server, you can create an account in their free public server and start using eyeOS right now. Just go to eyeos.info and discover the power of eyeOS

According to the author, "Microsoft has released it’s Windows 7 Release Candidate (Win7RC) and is making it available to, well, pretty much everyone! In the past, beta’s and release candidates would normally be released to IT professionals who had an extra computer kicking around to test things like this on. Yet, what if you just have the one computer at home and really want to test Win7RC, what do you do? Here’s the answer and it’s not as scary as you might think. Install a virtual machine (VM). What in blue blazes is a virtual machine you ask? Think of it as a computer within a computer. Then you can install whatever you want to test on it, without fear of losing your main operating system and the files on it. I’m going to outline the installation of Sun’s VirtualBox. There are quite a few VM’s out there, I just chose Sun’s since it was recommended to me by a friend who is vastly more knowledgeable about computers than me. Yes, it’s true. Someone knows more than me. Okay, most people know more than me."

According to the author, "Since my last article you’ve been sitting there with your freshly installed virtual machine, just waiting with baited breath to install Windows 7 Release Candidate. Wait no more, my friend, wait no more. Now we’ll install Win7RC on your virtual machine"

Emulates a very early computer, 1951

MobaLiveCD is a freeware that will run your Linux LiveCD INSIDE Windows thanks to the excellent emulator called "Qemu". MobaLiveCD allows you to test your LiveCD with a single click : after downloading the ISO image file of your favorite LiveCD, you just have to start it in MobaLiveCD and here you are, without the need to burn a CD-Rom or to reboot your computer

DOSBox emulates an Intel x86 PC, complete with sound, graphics, mouse, joystick, modem, etc., necessary for running many old MS-DOS games that simply cannot be run on modern PCs and operating systems, such as Microsoft Windows XP, Windows Vista, Linux and FreeBSD. However, it is not restricted to running only games. In theory, any MS-DOS or PC-DOS (referred to commonly as "DOS") application should run in DOSBox, but the emphasis has been on getting DOS games to run smoothly, which means that communication, networking and printer support are still in early development. DOSBox also comes with its own DOS-like command prompt. It is still quite rudimentary and lacks many of the features found in MS-DOS, but it is sufficient for installing and running most DOS games

Sign up for the beta test of this new web based operating system. Thanks to gHacks

Boot multiple live Linux distros from a usb flash drive .....(free).....

Experimental OS. LoseThos is a 64-bit, multicored, multitasking, open source, public domain, ring-0-only, single-address-map operating system for the IBM PC. It requires a 64-bit x86_64 CPU and 512+ Megs of RAM. It does not have GPU acceleration, so I limit it to 640x480 16 color graphics. LoseThos will run natively, either stand-alone or dual booted. The easiest way to dual boot is to install on a 2nd hard drive and select which to boot with the BIOS. Use LoseThos' installer to install onto a partition. LoseThos has an optional master-boot-record boot-loader and can partition a drive if necessary. YOU CAN'T COMPILE WITH OTHER COMPILERS. Use InstallBoot() to make, if you like. The vision for LoseThos is a 64-bit Commodore 64 that's a thousand times faster than the original and has a shell that is C/C++ instead of BASIC. It's for recreational programming. The reason you would pick LoseThos over Linux is that it is only 129,242 lines of code, so you can easily tinkering. LoseThos isa secondary operating system you will use in additional to Windows or Linux because LoseThos does not have networking .....(free).....

FreeNAS is a free OS to create your own NAS Box.

Free Pre-Built Virtual Appliances, Uncompress and load into VMWare Player

OpenThinClient is a Free Open Source ThinClient Solution consisting of a Linux based operating system along with a comprehensive Java based management GUI and server component. It is intended for environments where a medium to large number of Thin Clients must be supported and managed efficiently. Offering flexibility unheard of in the world of proprietary Thin Client Solutions, openThinClient empowers developers and integrators to create advanced Thin Client solutions... for free

WinToUSB is a free software that allows you to install and run Windows operating system on a USB hard drive or USB flash drive, using an ISO image or CD/DVD drive as the source of installation. WinToUSB also support creating bootable WinPE USB drive, it can help you to transfer the contents of WinPE to the USB drive and make the drive bootable.

Ophcrack is a free Windows password cracker based on rainbow tables. It is a very efficient implementation of rainbow tables done by the inventors of the method. It comes with a Graphical User Interface and runs on multiple platforms.

It is a very basic V2P free tool to simply dump a VHD contents/structure to a physical drive. It designed to work only with dynamic VHD like Disk2vhds output.

OpenMediaVault is the next generation network attached storage (NAS) solution based on Debian Linux. It contains services like SSH, (S)FTP, SMB/CIFS, DAAP media server, RSync, BitTorrent client and many more. Thanks to the modular design of the framework it can be enhanced via plugins. OpenMediaVault is primarily designed to be used in home environments or small home offices, but is not limited to those scenarios. It is a simple and easy to use out-of-the-box solution that will allow everyone to install and administrate a Network Attached Storage without deeper knowledge.

Active KillDisk Linux Console is an easy-to use and compact utility that allows to sanitize storage media using more than 23 international data sanitizing standards. It erases permanently all data on Hard Disks, Camera Flash Cards and USB disks, SCSI storage and RAID disk arrays even in parallel mode (several disks at the same time).

Redo Backup and Recovery is so simple that anyone can use it. It is the easiest, most complete disaster recovery solution available. It allows bare-metal restore. Bare metal restore is not only the best solution for hardware failure, it is also the ultimate antivirus: Even if your hard drive melts or gets completely erased by a virus, you can have a completely-functional system back up and running in as little as 10 minutes.

UPDATE: Site no longer available but MajorGeeks still has it, select the MajorGeeks Mirror to download. This new tool allows an easy and comfortable way to download genuine Windows 7, 8.1 and 10, as well as Office 2007, 2010 and 2011 disk images (ISO) directly from Microsoft's servers.

A great android emulator to play Android games on PC. One of the fastest available, with great play store compatibility. Free, but loading screen adds that do not get in the way. Also has an app store link to a sponsored app when loading that is not annoying.

WYSIWYG Bash Prompt customization for linux bash. Pick your options and colors and insert the result in your ~/.bashrc

tmux is a terminal multiplexer. It lets you switch easily between several programs in one terminal, detach them (they keep running in the background) and reattach them to a different terminal. You can install using most package managers like apt.

Open Source modern cross-platform data manipulation tool for Microsoft SQL Server, PostgreSQL and MySQL