So, you deleted the file. Done. Wrong. When you wish to delete any sensitive information, you want to be sure that it will be deleted permanently.

“Basic deletion of a file does not remove the data, but simply renders it unreadable by the operating system  . This is why System Restore can resurrect file data to restore an operating system to a previous time. When data is basically deleted using the delete key or selecting Delete from a dropdown menu, a shadow copy is left behind. This shadow data that is left can be accessed by malware and hackers easily. For sensitive data deletion, you want to be certain that the data is completely wiped. Having a portable application capable of doing this is a bonus, particularly for the travelling user.” – gHacks

(image from gHacks)

If you need to know for sure that no one can never ever read it, an ordinary deleting of files isn't enough. There are 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 replacing of the actual content with some data, and by doing that “overwrites” the original.

“Freeraser can function on three levels:

1. a fast destruction (standard 1-round filling of random data)

2. a forced destruction (3 rounds of filling according to DoD 5220.22M standard)

3. an ultimate destruction (35 rounds of filling with data according to the Guttman algorithm).

It is obvious that the more powerful destruction is performed, the more rounds it takes and the more time it needs.

Users can define the method that they wish to destroy their data with.” – Freeraser

It is portable, and resides in your systray. You can customize the degree of transparency.

Support: Vista, Windows7.  I do not know about XP.

Download:  http://www.codyssey.com/products/freeraser.html

Read more here:  http://www.ghacks.net/2011/09/17/portable-permanent-file-deletion-with-freeraser-file-shredder/?_m=3n%2e0038%2e280%2ehj0ao01hy5%2ea7n