When I add an .avi video to my powerpoint presentation the still appears
fine
but when it plays it disappears.
One of the most frequent reasons for this is the pathlength, which should
not be more than 128 characters (for network path AND filename). Try to
move your presentation and the video to a folder like C:\test. Shorten the
filenames (if you rename the video, you have to re-insert it).
Best regards,
Ute