(sorry for my bad english)
I've tried this test:
i used "disk redactor" ( http://www.cezeo.com/products/disk-redactor/ ) for wiping my system hard disk (selecting "no last 16K wipe") ... this tool simply writes a big file as huge as the free space at the moment is.
Then i used recuva that listed a lot of files that can be recovered at "excellent" state... obviously that's not true: the whole of the space was overwritten.
That tool is only one of many of these available in the net (freely).
Bye!