There is a bug in XP media summery page. It show the combined
KBytes/seconds rate of the media file (not just the video part). Example you could use GSpot to get all kind of information about a media file (
http://gspot.headbands.com/gspot252dl.html )
edit: the bug is not the KBytes/sec (which is just unusual), but that the combined (audio+video) data rate is show for the video.