I'm giving a old computer to someone and I was wondering what is a good way to cleanly format a hard drive in a way that will make data recovery impossible. (Yes I am that paranoid.)
By default the formatting ability through Windows does not completely remove all traces of files. You would need to buy a software package that does it. Here is the type of program that should do what you want: http://www.stompsoft.com/drivewasher.html
I recommend this, Darik's Boot and Nuke. It is VERY thorough. It rewrites the bits on your harddrive a few dozen times, so it takes a while. http://dban.sourceforge.net/
Why not just buy a new HD for the computer? It would probably end up being cheaper than buying the software, unless you have multiple drives you want to wipe out.
Well, my friend knows I have a old drive in there. If I bought a new one, it would look like I'm hiding something from her. And no, I'm not crazy about sharing p*rn with a girl. I'll never hear the end of it.