So the damage is only cosmetic, but you replaced it anyway?

Anyway, you'll definitely want to wipe the drive as thoroughly as possible. Really, it's not something that you can do too much of. If you still have the discs that came with the system, I'd just restore the system to the exact same form it was in when you got it (after wiping it as mentioned above). Can't help you with how MS's nonsense works, though.