I've been helping out some of my friends with their computers, which they were getting ready to sell and came across Kill Disk. With Kill Disk you can be sure that the files on your hard drive are erased well enough, so that no one can recover them. Great for any computers that may have very personal information on it. It should work with just about any computer, no matter the operating system or size of hard drive. There are different versions, including a free version that allows you to do a one pass zero method. You also get updates from Kill Disk free as well. If you chip in some money for the paid version, you can do up to 99 passes on your hard drive (making your data harder to recover) and it writes over your drive with algorithm's that support 17 security standards.
Kill Disk uses your bios to delete your hard drive, which means you will have to boot from your Kill Disk CD. Check it out for your self because it is especially important that your hard drive is clean a and safe from thieves. Here is the link: Kill Disk. If you have any questions about how to use it or have any other hard drive erase methods please leave a comment. Thanks for reading.