From Nikhil Baliga:
When a file is deleted, it is not completely removed from the hard disk. So, it is actually possible for somebody to recover these files using file recovery programs. This is a threat if you have some sensitive data that you wish to remove. Shredder is a freeware program using which you can simply select files and shred them. With a very easy-to-use interface, just select the files, and click on shred.
The files once shred, even if recovered will not show the original contents. The main advantage of this program is: It's just 9 kb in size (That's right 9 kb), and no messy forms, just one simple dialog. Attractive Matrix type Green interface. Bug fixes and new features: duplicate entries removal works, duplicate entries get removed automatically during shred or erase, sequences of 0s and 1s get filled in, before use of standard Nikhil Baliga's Shredder algorithm (that was used before), refresh feature has been added, and speed has been increased.