I just spent HOURS trying to get a Windows .avi file of a screen recording to work correctly on my Mac. Perian didn't work, neither Quicktime would work - the audio simply wouldn't play. After trying LOTS of conversion programs and even pro software (Premiere, Final Cut) I was about to give up. I'd almost had it working with Tune4Mac, but it turned the whole thing orange!
I found mention of this on a website, and in 2 minutes had beautiful working .mov files, audio and video working, and perfectly in sync. Thank You!