Deleting and formatting will not remove the files, only the pointers to the files. Anyone with access to the Internet and half a brain can recover every single file.
There are people and software that can even recover files that have been overwritten with zeros. I believe DOD now says that shredding the hard drive is the only valid way of making data unreadable. Short of that, here's a list of free tools. I have used Eraser before:
http://www.thefreecountry.com/securi...redelete.shtml