Hi William
It could be missing codecs.
There is a freebie called GSpot that can check for you
(http://www.headbands.com/gspot/) (for how to use see:
http://www.windowsmoviemakers.net/PapaJohn/68/Gspot.aspx).
Also check the file path length. Try creating a folder on your C drive,
moving PowerPoint and avi file to it, then reinserting the video.
I normally run videos through Plays For Certain - you might like to give it
a try if you use videos a lot: http://www.playsforcertain.com/index.html.
Unfortunately it looks like their great video tutorial is till down :-(
Lucy
--
Lucy Thomson
PowerPoint MVP
MOS Master Instructor
www.aneasiertomorrow.com.au