Secure Formatting Disks [closed]

http://www.dban.org/

Darik's Boot and Nuke ("DBAN") is a self-contained boot disk that securely wipes the hard disks of most computers. DBAN will automatically and completely delete the contents of any hard disk that it can detect, which makes it an appropriate utility for bulk or emergency data destruction.

It does a good enough job. Like jldugger said it's enough to write 0s to the drive, you could always smash it with a hammer and take out some frustration about "that one user" shrug

See: Sugestions for cleansing PC's before recycling / disposal

Also see How should I securely wipe data from a hard drive?

Use the free Eraser software to securely remove sensitive data from your hard drive. You can even choose the data wiping algorithm and the strength of the erase making it almost impossible to recover your data.