Ok, here I go. First uninstall all codecs you have right now and start off clean. Now, the first one you want is divx which you can get here (Just get the standard codec, not the ad-supported one). The next codec you need is xvid which you can get here. The last codec you need is ffdshow which you can get here. Just install all these codecs and play them in a good media player (WMP, Divx, VLC) and you should be fine. Hope I could help.