have you already hacked your phatbox? if not you'll have to send the drive to phatnoise for repair, or borrow a working original dms from someone, or buy one on ebay or something. Once the keys are gone from the begining of the drive they are not recoverable.. if you repartitioned the drive, which is what it sounds like happened, then those keys are gone and the drive wont work in a box till it is repaired by phatnoise or you hack the box with a working DMS.
Phatnoise has a bootable repair CD available on their website someplace. I don't have the link handy.