I'm surprised your QT couldn't play them. Mine can but I have xtra QT plug-ins (codecs). Try VLC (it's free) http://www.videolan.org/ (it also plays vcd's, dvd's, divx, & more.) Just use whichever mirror site (I used France.) There's also MPlayer: http://mplayerosx.sourceforge.net/ Actually, DivX can create a form of avi so that may complicate things. But the above 2 players should be able to play them.

AVI stands for Audio Video Interleave. It is a special case of the RIFF (Resource Interchange File Format). AVI is defined by Microsoft. AVI is the most common format for audio/video data on the PC.