I've had similar problems playing avi or mpg files, but the weird thing is that I sometimes cannot play files emailed to me by my father who is using my old Performa! The difference here is I am using OS X 10.2 (QT6) and he's using OS 8.5 and I believe QT4 or 5. That one really confuses me, that my old computer can play it, but my new one can't. Dave.