hi guys, could someone help me with my problem?

i'm having difficulty playing an anime avi which i just finished downloading yesterday... there is no sound, only video. i used Gspot to identify the codec needed to play the audio or sound of the file; and it appears that the codec needed is Mpeg layer-3 audio codec, which i have installed in my computer, but the problem is no sound is coming out when i watch it. i also have AC3 and AAC installed in my machine.

What do i need to do? is there still anything i need to install to make it work? anybody?