Permanently deltete a file

While it is possible to retrieve a file that has been deleted from the recycle bin, it is not something that an ordinary user can do easily. To completely delete a file there are a lot of software programs on the market that can help. I like Norton's System Works. I use 2005, but really anything after 2001 is fine. Norton's has a program that uses the US DOD (Dept of Defense) standard to delete a file. Not only is the file deleted the portion of the hard drive that file is located on is written over with 1 and 0's 7 times. This guarantees that the file is gone.

Once items are deleted from the recycle bin, the files are only marked for deletion. This tells Windows that it can overwrite the file if it needs to. For most home users, simply emptying the recycle bin is good enough, however, for a tech savvy person, recovery of the file is fairly trivial provided that it has not been overwritten. To prevent this there are utilities which will overwrite the free space on your hard drive with 1's and 0's in various patterns to obliterate remaining data. If you're really paranoid about these files here's some software (free and otherwise) that will help http://tinyurl.com/9u5u2

Eraser is a free program for Windows that will do the job well. You can erase current files, or overwrite "free space" where files were already deleted.
http://www.heidi.ie/eraser/download.php