I had the same problem, no you are not missing the audio file, it's embedded in the AVI. I think the problem is the AC3 codec, if I recall correctly installing the AC3 codec didn't immediately work, but afterwards I installed ffdshow to identify that this was indeed the correct codec and somehow this fixed the audio for me. Failing that you can burn it to a DVD and watch it in your PS3 no problem so long as you have the latest update.