One of the people at my forum sent me a video off of an Xbox Diagnostic disc. It's an old marketing video from long before the xbox came out. Lots of early footage from a bunch of different games. All of the videos come from Microsoft Studios, i think...
You can grab both a low rez (2 meg) and a full divx (22 meg) copy of the video here:
http://gamerhistory.com/forum/viewtopic.php?t=530