Deleting Files Permanently From Hard Drive?

So, I used Pandora Recovery to find the files, recovered them to a folder on my desktop, then used Sure Delete and File Shredder, ran Pandora again, and low and behold, there they were again. What gives? I thought these programs were suppose to "Permanently Delete Files"? It's personal financial info that I don't want on a certain computer. I've gotten burned before, and I don't want it to happen again. So, what can I do to insure that these files get permanently deleted and some cracker jack program like Pandora find them and let someone access them? Thanks.