I don't agree with you. Logically a tool either works or it does not. So, it is theoretically possible that I could run several tools and still be exposed?
From a security viewpoint the correct approach is to delete your data and then use data recovery software to see if you can get it back, or see if it ever existed.
When I worked in the defence sector, one person would erase a drive and a second person would audit that erasure. Both would have to sign the task off.
;)
Try this:
http://www.recuva.com/download
And this:
http://www.theabsolute.net/sware/dskinv.html
All
free and I use them myself :D
On a personal note, unless stuff is really confidential and you are sure that you have finished with it, I usually recommend that you just delete it. That way you can recover it (hopefully) if needs be.
Every now and then I use the "wipe freespace" option to make sure that the drive is clean. This will make deleted files irrecoverable, but I should have found out that I still needed them by this time.
When I am wiping a drive before a fresh install of an OS I prefer to use the HDD manufacturer's tool, as this will also do some drive checking as well as the wipe, and a simple overwrite is adequate for reinstallation.