This is getting silly.
For the average person any security wipe utility that conforms to DOD 5220.22-M standard such as EraserDisk -
http://www.micro2000uk.co.uk/product...k/features.htm - is enough.
The idea that someone who picks up a tossed hard drive from the dustbin put out by No 10, The Elms and finds it properly security wiped is going to go to the time, trouble and very considerable expense of dismantling it and searching the platters for half a dozen random bytes that might or might not be you PIN code or your pr0n collection is risible.
Far cheaper and easier to break in and pinch your plasma TV, your bank records or for that matter the entire PC. Far easier and cheaper to hire a pro hacker to craft a handmade exploit to root your system and download the lot!
Scraping dubious data off wiped hard drives is only viable if you have a majorly urgent need for national security or commercial advantage, lots of time and lots of money. Even then it recovers only scraps which need other intel to be useful.
Get a grip folks!
Mac