Fill up your hard drive. Why? Some old applications and games won't install or work properly if they detect that your hard drive has more than 2GB or 4GB free, depending on how they were written. This is because those programs were written in the days when most people didn't even know what a gigabyte was. Another reason you might need to temporarily fill up your drive is that developers often have to stress-test their applications or installer routines to ensure they work gracefully when a PC is very low on disk space. Finally, the only way to truly permanently erase data on a hard drive is to overwrite it with other data. Simply reformatting your drive is not enough.....(free).....