From lastest 2007 firmware update
http://www.xbox.com/en-US/support/sy...4-features.htm
Improved playback performance for h264 720p .MOV files
Improved playback performance with 1920x1080 MP4 files
Improved playback performance with 5Mb h264 encoded video files
Improved playback performance with 60fps 720x480 MP4 content
Improved playback performance with h264 files in .m4v containers
However I cant see .mov or .mp4 files under XMC or Video blade in dashboard