Yea this will do that. That is known as Wipeing.
I use a wiper all the time. I have mine set to DOD standar of 7 wipes when it deletes a file. That means it writes over the file with random ones and zeros. If you just delete it is kinda (quoting Tech TV) like riping the index page out of a book and saying you got rid of all the info in a book.
See links below http://www.chez.com/bedrettin/wipe/ http://www.jetico.com/bcwipe.htm
Matter of fact just bookmark this mother [censored]... http://www.jetico.com/
That last one should about cover it.
What the first program I listed dose is pull up files you have "deleted". If you install it and run it to look at the C drive. Everything red has been deleted. So you thought.