I have QT 7 and when I try to run .avi files, video plays effortless, just a bit stop & go and times, and also at the beginning only 2 secs of audio then nothing. Try using VLC Player. VLC can run basically everything. Video_TS, .mov, .avi and just all you'll ever come across. But I'm not sure if its available for MAC OS 10.2.8 and under... hm... you'll need to check.