Is it possible to recover data from a hard disk drive that has been overwritten with zeros? This is the question behind the The Great Zero Challenge that starts today.
There are some rumors telling that it could be possible to recover data under that conditions with the help of highly specialized and costly equipment. For example the read/write head won't exactly align with a track's centerline on every seek operation. Using something like a magnetic force microscope it could be possible to recover patterns of "old" bits that are left over on either side of the centerline. Of course one would have to open the hard drive's enclosure and process the platters in a clean room. Unfortunately that's explicitly interdicted by the rules. Under that conditions it is highly unlikely that this challenge will bust (or confirm?) the myth.
17/01/2008: The rules now allow established US-based data recovery laboratories and agencies to disassemble the drive.
I doubt anybody will enter such a challenge for ... a $100 prize!
(unless it gets very broad press coverage)