Playing MPG movie files via the Xbox 360.

I have a number of video files that were recorded using a Sony digital camera
(not a movie camera). They are in the mpg format.

Now, when I tried to play them on the Xbox360 they weren't recognised as video
files, so they weren't displayed in the file list.

I then tried to play them on the PC. Windows Media Player Ver. 11 would play
them but the sound was breaking up and there was no video.

I then opened them using Apple Quicktime and they played fine. Just as they did
with Nero Showtime.

Now, the Xbox will play whatever media files on my PC that is in the WMP11's
sharing library. Except it won't play these mpg files.

Short of converting them to divx/xvid AVIs or WMV files is there a way that I
can get them to play on the Xbox?