ac3, media players - "performed an illegal operation"

I’m new with all of this, but I’m having the hardest time trying to watch this movie! I used GSpot and I learned I needed an ac3 codec. So I downloaded it (by using the links from this website). But when I try using a player such as zoom player or divx or wmplayer, i get a “performed an illegal operation” notice! When I uninstall ac3, all 3 apps work fine, but again, there’s no sound! Can anyone help me?