Codec prob

I try to watch videos on WMP but sometimes it says Windows Media Player cannot play the file. One or more codecs required to play the file could not be found. Do I need Xvid or Dvix

is it a .avi file, if so then yes you do

Ok I have it how do i use Dvix.

right click on the .avi file. click "open with" then go to choose program then browse then open up where you installed divx and double click the .exe file and click add (or something) then click the little check box saying "allways use this program for all files of this type" then it plays