UPDATE:

We now recommend that you use a program called DBAN in order to erase your hard drive.

Please see this article: Completely Erase a Hard Drive with DBAN for details.

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When you delete a file from your hard drive, it's not completely erased. Similarly, when you format a hard drive, the data can sometimes be recovered.

If you give an old PC to someone else, or donate it to charity, it makes sense to completely destroy any data on your hard drive. You certainly don't want your sensitive financial information to be recoverable under any circumstances. With a simple floppy disk and free software, you can have that piece of mind.

The Secure Harddisk Eraser is a way for you to completely erase that data. It overwrites every sector of your hard drive with zeroes, thereby eliminating any data that may be hiding. But it doesn't do this only once -- it does it 3 times! That it is the standard that the US Department of Defense recommends. But if you want more security, you can have it overwrite your hard drive 35 times!

You can create the disk by downloading the floppy disk image from the website. A floppy disk image is basically a file that holds all of the information necessary to create a floppy disk that has the software installed on it. To use the image and create the floppy, you'll need to use a utility such as WinImage.

If you are interested in trying it out, be aware that this is a completely irreversible process. Be careful when using this disk! And if you have questions, post them in the Q&A Forum.