If you want to really delete all your data, you can download "file shredders" that will help. There's one included in Spybot S&D. They will overwrite the file being deleted with several different patterns making it nearly impossible for anybody to recover the data that was originally there.
If this is XP, why not create a new user for your friend and just delete the user account you used? Then, make sure any applications that stored data files (like quicken, turbotax, etc) in their program directories, remove those data files and account information as well. And also go through the registry and delete any stored history and personal settings.
It's not foolproof, and you can find a shredder that will shred all the free space if you're worried about it (and it's probably a good idea to do that).
A reinstall is the safest thing to do, but you'll still want to shred the free space after the reinstall. (ok, the super safest thing to do is to destroy the disk, but if you're diligent, and find everything, it should be ok.)
Newegg has the Seagate internal 2.5" 80G IDE drive for around $65 if you want to go the other way and reinstall onto a clean disk. Maybe you can get your friend to pay for the new hard drive?
-David
Last edited by LIH Prem; Feb 10, 2007 at 8:07 pm