I'm sure there is someone out there that has upgraded the drive if it's possible. Phrase a terse, natural-lanuage question at ask.com and see what hits you get - something like this: How would I upgrade the hard drive on a "My Book"?
.bh.
PS: Avoid the word 'hacking' as much as possible when posting your thread starters if you don't want your posts given the hairy eyeball... .bh.