MP4 files play with a green screen and messed up

MP4 files play with a green screen and messed up.
What should I install to fix this?
This is in Media Player Classic and VLC.
I tried installing 3ivX, that didn’t fix it, though without 3ivX, DivX files have the same problem. (I uninstalled 3ivX then reinstalled it to find this out.)

Don’t guess to make it working. Download GSpot or Avicodec and open your file with one of them to find out what codecs you need to play it. Avicodec has a “web” tab for audio and video. Click on it. http://www.free-codecs.com/