How does Windows Media Player choose video codec?

I'm running Win XP SP3 and Media Player 10. I would like to force Media Player to use a certain mpeg4 decoder (the one from DivX), but for some reason this is not the codec Media Player player prefers. I've been able to force it to use the DivX codec by finding the actual DLLs for all the codecs ahead of DivX in the preference order (two of them) and moving them.

I'm assuming the preference order of codecs must be specified somewhere, I can't find where that is. Does anyone know?

Thanks!

 

If you recode all the movies with that codec, the media player will use it for playback. Each codec has it own method / mathematics behind its compression - you can't use any codec to open any movie.

 

I'm specifically talking about the case when multiple codecs can decode a movie. I'm assuming this must be the case, if I'm able to change the codec WMP uses by "taking away" the codecs it prefers by moving the DLLs. I just want to change the order of preference.