I've had good luck using ffdshow codecs. Here'* a download link - see if it helps.

http://www.afterdawn.com/software/vi...rs/ffdshow.cfm

i dont know if you solved this but when you try playing it in wmp right click it and if you go to error details see if you can download just the codec, thats happened to me before and once i get the codec they usually always play unless it likes to be dumb

find an "All-in-one" codec pack from a respectable lookin site.

Yeah...watch what codec pack you install. Some of them can screw you over, especially if you have old codec versions lingering. Get the program called "G-Spot" and it will tell you what codec you are missing to play the file.