Deleting files in Windows doesn’t really remove the file. It just removes the reference to those files which means a data recovery program can still restore them. If you are worry about leaving information on your computer or throw/sell your hard disk, this cleanup program can help you and it will completely destroy data stored on the device.
Eraser (http://www.heidi.ie/eraser/default.php) is a secure file deletion tool that allows you to completely remove sensitive data from your hard drive by overwriting it several times with sophisticated patterns (Gutman, USDoD and others).
It is easy to use. You can simply drag and drop files/folders onto the on-demand eraser, use the convenient Windows Explorer right-click extension or use the built-in scheduler for automated wiping of unused disk space, browser cache files etc.