As you may already know, there are a lot of free and commercial undelete programs available on the internet. You may wonder how those undelete programs can magically bring back deleted files. Well, that's not really magic at all. When you empty the recycle bin in order to remove deleted files from your hard disk permanently, Windows does not actually remove them. Instead, for performance reasons, Windows simply marks the location of deleted files on the hard disk as unoccupied and reserves them for future writing. Hence, until Windows decides to write new data at the same location as deleted files, those files theoretically still exist on the hard disk. If you want to recover deleted files from the hard disk, simply scan through all unoccupied areas in your hard disk and try to find data that matches the profile of the file that you're looking for. When you find them, write those data into a new file. This is how an undelete program works.

So, what should I do if I want to remove a file immediately (permanently) from my hard disk? That's easy, all you have to do is force Windows to write a new data at the same location of the file that you want to delete. This is how a secure delete program works. Currently, there are several algorithms that can be used to overwrite deleted files securely. TweakNow SecureDelete supports two of the most commonly used algorithms: Gutmann and DOD 5220.22M. In addition, the program also supports overwriting deleted files using a series of random characters multiple times. This method might be less secure, but it is faster than the other two methods and still safer than the standard Windows delete method.