how do i uninstall xvid and divx codec .. ?

i got a game and had an error somebody described it this way that:

Okay, for those of you getting the black screen at the beginning of the game, uninstall divx/xvid codecs. the game thinks your avi's are now divx codec and cannot read it right. they are mpeg2 avi's but the game goes retarded if you have divx/xvid codecs.