Any of the heavy, multi-pass drive cleaners will do the trick. Make sure it has a feature to clean the clear space on your drive. Ace Utilities is a nice product and unless you do something really strange there is very little danger of eliminating files that you really need. Windows Washer has a pretty nice package for securely wiping any trace of old, deleted files.
data shredder - customizable number of passes
http://www.cbltech.com/data-recovery/software/data-shredder.html
East Tec Dispose Secure , Active Kill Disk Pro or Dariks Boot and Nuke this one is free and you can get it here http://dban.sourceforge.net/
Any of the heavy, multi-pass drive cleaners will do the trick. Make sure it has a feature to clean the clear space on your drive. Ace Utilities is a nice product and unless you do something really strange there is very little danger of eliminating files that you really need. Windows Washer has a pretty nice package for securely wiping any trace of old, deleted files.