someone else will come by to give a better answer than mine, but for the time being i'll tell you what little i know:
sounds like a codec issue. you don't need to use windows media player to view avi's. several vid software options out there but i use irfanview (
http://www.irfanview.com/) and if i get a viewing error, it usually tells me what codecs i need to find and install.
and if anyone knows how to view wmv's without using windows media player that would be cool to learn. fuckin hate wmp.
(p.s. moved to "surfing tips" as this is not peachy related).