Your best bet would be to hang out a while at the QuickTime Forum at Apple. Most of the problems you encounter have been dealt with countless times: you will find many posts.

An .smi is a self-mounting image file in X. It should mount as a volume on your desktop just by clicking on it. If that doesn't work, the Indeo codecs are listed at versiontracker.com. You need all of them. DivX Doctor only runs in 9, not X. It also does not require the information at the end of an .avi file. I've used it to preview files numerous times.