YUY2 codec, huh..........

I had an .iso file that I somehow converted to an .avi (i've tried and dL'd so many things that I don't know how it even happened).

Now, finally, I can play the file in Windows Media Player, Divx, Real, and about 3 others I tried.

Problem: play back is choppy, slow motion, pauses and restarts. Cuz of this, the audio and video don't sync.
Even though WMPlayer opens and plays the file.......it gives me a codec error. It says I need the YUY2 codec and directs me to a service pack for Windows XP (I've got 2000).

Web searches keep leading me back to this :http://www.fourcc.org/fccyuy2.php - the problem with this is that I don't understand the instructions. I tried to get the Indeo from Intel but I can't find it. And my computer doesn't have the path this guy is recommending to install too.

I've also tried reducing color quality and lowering resolution. I've tried Virtual Dub, but nothing seems to make the choppiness go away. Cuz of this I believe I need this YUY2 thing. Anyone????????????????????