Somehow I've totally messed up my computer to the point where it will no longer play .avi's or dvd's using any player software... I tried downloading Bsplayer .. divx .. wmplayer .. nothing works

What happends when I try to play a dvd or click on an .avi is my computer goes to 100% cpu usage and the movie will not play in the player and ends up showing as not responding in task manager.

I've tried to roll back to an earlier date but that did not work.

I am pretty sure I messed up something while downloading a codec pack.

I dont know how to fix this .. and my wife is about to freak because she cant watch her dvd's ...guys.. please help me out.