.AVI screeching noise for audio problem!

So in most instances, whenever I view an .AVI movie file, usually with Xvid encoded, the audio is a very loud screeching noise. I figure it must be a codec missing in the AppleTV (black) package and am wondering how to fix this. Any help is appreciated.

Are you connected to an AV receiver or just a TV?

You may try disabling the AC3 and DTS audio options found in the Media --> Settings --> Playback menu.