Codyssey.com - Free shredder
http://codyssey.com/

An ordinary deleting of files isn't enough! When you wish to delete any sensitive information, like industrial secrets or some unwanted content, you want to be sure that it will be deleted permanently. Sorry to say, there is a plenty of software recovery tools that can restore your deleted items. If you need to destroy any data and eliminate any possibility of its restoration you need a "shredder". This software destroys the data you choose before the deletion, using a complicated procedure of filling the actual content with random data.

Free document shredder (download)

Hard disk erasing utility (so deleted file cannot be recovered). Similar software: "Eraser", see http://www.heidi.ie/node/6