You need an AC3 Filter codec to decode the audio on the AVI movie file. So if you ever download an AVI or DVD movie from the net and there is no sound on the file, you need also to download and install the AC3 Filter. Once installed, all your video players (Windows Media Player, Winamp, etc.) will be able to play the audio on the file. The latest version is 1.09a which is still in beta. The 0.07b is the last stable version.