you don't need a modded xbox to play it early. A lot of ppl have been streaming legal copies that they obtained illegally. Mom and pop stores have been selling this shyt. The game comes with two discs and I think micro shipped Disc 1 (campaign) early, so that is the only copy that you can find. I heard a few ppl who got it will get disc 2 (multiplayer) later on today.
edit: I gotta find out if micro gon be banning nikkas for playing it this early. This local joint will be getting it early. Gave em my math, so they will be calling me when the shipments come in. I'm not trying to get my box shut down though, fukk all that. I want the game now though, it's muthafukkin HALO.