I downloaded Recuva and made a scan of my C: and D: hard drives. I found an impressive amount of recovered files, but when i tried to delete them, Recuva told me:
Deleted 0 file(s) in 0.01 sec(s)
I'm using Windows XP home, service pack 2, Recuva 1.11.257
Are you checking or highlighting the files to be securely deleted? If you are highlighting and selecting Delete Highlighted then your mouse cursor must be over the highlighted area, else you get the 0 files deleted message. Very small files held in the MFT will also not be deleted, but in this case there will be a message saying so.
I am on the same spec as you and secure delete works OK - on one file anyway.