If you want to get rid of a very sensitive photo or document, you can set it to fire and nobody will be able to recover it. But when it comes to sensitive electronic files that exist on your hard disk or USB keys, it is not very easy to erase them so that they cannot be recovered anytime later. Anybody with special software programs like Recuva can easily recover the deleted files from your disks of they have not been overwritten. If you want to delete your files irrecoverably then then only solution is to overwrite and rename a file multiple times before finally deleting it. A free program BitKiller can do this for you. It can overwrite files with garbage data multiple times and then deleted them after the files have been renamed many times.
You can get BitKiller from its sourceforge website. The download is a very small portable program that can be run right away without any need of installing it first. Its portability makes it easy to carry with you in your USB flash disk.
Using BitKiller is very easy. First you have to add files or folders that you want to get rid of. You can add as many items as you want. Then you have to select an overwriting method for the files. You can choose from simple zeroing, random data, DoD 3-pass, DoD 7-pass and Gutmann 35 pass methods. If you are using a SSD disk or Flash disk, then you should avoid Gutmann method as it can reduce the life of your disks.
Finally, you can click on the Shred Files button to start the shredding of these files. After a few confirmation prompts the shredding starts and a progress bar shows all the files being shredded. In a few minutes, all the added files or folders are destroyed beyond repair.
Conclusion: The BitKiller program is a small, portable and effective file shredder. It can delete your files irrecoverably so that they cannot be restored even by file recovery software like Recuva.
You can download BitKiller from http://sourceforge.net/projects/bitkiller/.