From here - http://www.thisblogblo.ws/destroy-your-data/ via digg
Most of the time you want to avoid destroying your data. But eventually you will actually want to destroy it. For instance, if you were selling your hard drive, complete PC or Laptop on such a service as Craigslist or eBay; you would want to make sure that person doesnít have access to your files, email or personal info. Even if you fdisk your drive and format it, thatís not enough.
I canít tell you how many times Iíve bought computers or drives full of this information. Fortunately for those people, Iím not malicious. And fortunately for you, Iím going to show you a great program.
(Check out this article on destroying data on memory cards from digital cameras, phones, etc.)
Darikís Boot and Nuke! DBAN for short.. This little program packs a mean punch and will completely wipe your disk based on your preference of level. You can download in either floppy or CDrom formats. Once you boot up you will have some options (please make note of the warning!):
Typing in autonuke and pressing enter will wipe the data on every disk in the system its booting in with the DoD Short Pass method. Thatís 3x pass, which should be good enough for most people.
Pressing the enter key will present you with this screen:
Press the space bar to select the partitions and/or disks you want to wipe. (Selecting the disk itself will automatically select all the partitions on that disk):
Next press M to change the method (if desired). From there you can choose all sorts of modes including one that will wipe it and write data 35x!:
After choosing your method you may want to change the rounds. This will be on your comfort level. Press R on the main screen. You can choose from 1 to 999999999 rounds. Although I donít recommend the latter because not only will it take just short of forever, but itís probably a bit overkill!:
After that you can modify the verification settings by pressing V, but the default is to verify the device is empty after the last wipe. So you probably donít need to modify that. To start the wipe process, please F10.:
Thatís it, after a long time (it all depends on your disk size and method, but Iíd start this at night then go to sleep!) you can get rid of that old PC or hard disk and not regret it!