I made a short edit of some HD footage from a conference last year. The video is 1280 x 720 in MP4 (.m4v). I'd like some people at my office to see it, but they have Windows XP as well as corporate security that prevents them from loading any software (like Quicktime for Windows) onto their machines. So I assume the only player is the Windows Media Player in Windows XP. What should I convert my video to so they can play it and see it in HD?