You're right, I'm not sure what xbox has to do with Apple Support.
Your answer (via Google): http://en.wikipedia.org/wiki/Xbox_360#Multimedia
If your question was really, will xbox play movies you buy from iTunes Store, I am pretty sure the answer is, "No", because those have Apple specific DRM protection.
No. Xbox will not play .m4v files. Either xbox should support the file or - more appropriatly - iTunes should let you convert your movie to .wmv or a supported format. You can do that if you buy your movies or tv shows from any other vendor except for iTunes. I personally - while an avid Apple fan - hate the way iTunes tries to "protect" it's content by limited what the user is allowed to do with it. In the end they're only making the user experience more difficult, and less practical. Unless iTunes stops this rediculousness I think I'll start buying my movies/TV shows form Amazon.
Your hear what I said, Apple? Buying! I'm not trying to steal content, I'm just trying to watch it where I want in my own home! So rediculously frusterating.
I often play xbox, I usually play movies on xbox, download many movies from iTunes, I can break m4v DRM, you need a break in the DRM m4v software, Google to search to a lot of good software. https://www.google.com/search?hl=en&newwindow=1&safe=active&noj=1&biw=1440&bih=7 13&q=http%3A%2F%2Fbrosvideo.com%2Fm4v-converter.html&oq=http%3A%2F%2Fbrosvideo.c om%2Fm4v-converter.html&gs_l=serp.12...7365564.7365564.0.7366184.108.40.206.0.0.0.0.0 ..0.0.les%3B..0.0...1c.1.tVArSkRTudo