Ccleaner is a handy tool, but it doesn't do what vancouv wants.
It deletes all your internet history, downloaded files, junk etc, and it only takes a couple of seconds to run.
Cyberscrub overwrites any free space on your hard drive (up to 9 times, depending on the security required), and makes it totally impossible for any deleted files to be recovered.
On a mid range setting, it takes about 3-4 hours to totally scramble the free space.