i alraidy got mine.. its called the 360 :p
Altho, you need the version of windows that has Windows media center on it, witch is a total rip off, they should hand that program out for free. but yeah, i can copy stuff over to the Xbox, and play it from there. or i can just play it Directly from the computer, like i do with my music, and it will replace in game music :).
but if you are really heavy on wanting to have HUGE movies completly protable, you might want to get one of those, the Hardrive on the 360 is only 15 gigs i beleive. more then enough for all the patches and Demo's you could want, as long as you Delete the sucky ones.