Il n´y a qu´une seule version boulet 
J. Allard avait annoncé une possibilité, mais ce site minable l´a mal interprété.
Regarde une interview officiel:
Q: Will the Xbox 360 be sold in different models, one with a hard drive and one without? What about different sized hard drives?
A: It´s something we´re not ready to announce yet. We´ve been getting good feedback from people at E3 and a lot of retailers. Look at the success the iPod has had by having different offerings. That is something we have looked at, sort of on the long-term horizon. We want to go get everybody out there that likes to play, and make them an Xbox customer. how do we do that? I don´t think it´s a one-size-fits-all approach over the next five year horizon. I think we´ll enter the market in a very conventional fashion and from there it´s all about listening to gamers. That´s what we do. Until we have the first couple of million customers, it´s hard to say how we might further the audience.
Q: So the first Halo, or any Xbox title, won´t be backward compatible if you don´t have an Xbox 360 hard drive?
A: Yeah, it won´t work. Backwards compatibility is going to require a hard drive. We´ve been talking a little bit about la-la land, and saying, " Maybe there´s someday that an Xbox 360 doesn´t come with a hard drive."
Actually, the very first one we sell is goin to have a hard drive.
It doesn´t mean that the hard drive is always going to be attached. The owner can take it to a friend´s house, and the other people in the owner´s house can still use the Xbox 360 to play games.