as i said on #ps2newz
<Krizzz989> AVI files have something called a FOURCC code that determines what codec to use, to play the file. the fourcc code for a xvid avi is "xvid XVID". the fourcc for a divx5 avi is "divx DX50" you must edit the fourcc code of the xvid avi, to match a divx5 avi. to do this, use "AVI FourCC Code Changer" available here.
<Krizzz989> even though divx5 and xvid are two different encoders, they can use the SAME decoder, the divx5 decoder.
graphical tutorial attached.
edit: you can just type in the codes.