I just wanted to add that some rental shops use these discs, I used to work @ the biggest one, er.. you know the name...
Anyways, after a console is rented, this disc is that fastest way to put it back in original order.
Its green and it says "xbox hardware refresh disc", and something to the effect.
"this disc resets the hard disk, deletes saves, soundtracks, and settings"
there is another one too, that is REAL RARE, says "xbox repair and refurbishment"
"test equipment boot loader utility", man I was I had that one!