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First of all, you need to figure out if the problem is with the movie you are trying to play or your system configuration. You can do this by trying to play an MP3 or another movie and see if the sound works. If it does you should keep on reading for more information how to fix the problem. Otherwise you have to figure out what's wrong with your system configuration.

It's important to understand that video and audio are two separate things, which when combined make up movies. A movie consists of a video stream for the picture and an audio stream for the sound. The XviD codec is what makes it possible to decode the video stream, but it has nothing to do with decoding the audio stream. If the sound in a movie isn't working you have to find out which audio codec is missing and install it.

To find out which audio codec you're missing you should download GSpot and open the movie you are having problems playing. The program will give you information about what codecs are needed to play the movie and if you have them installed on your computer. However, please note that even though GSpot might say that you have compatible codecs installed this information isn't always correct. To see which codec is actually used to decode the audio, use the "Render" option at the bottom of the program. If GSpot says "Rendering failed" or "Partial failure" then you don't have any compatible audio codec installed, so you need to use audio codec name to lookup the codec you need to download and install in the following list:
 

Please note that the new DivX® codec doesn't include support for the DivX ;-) Audio format, so you won't be able to watch these movies with sound simply using the new DivX® codec. The only way to watch these movies with sound is either using the original DivX codec v3.11 alpha, or by installing the DivX ;-) audio decompressor separately.

Please note that  , if you  installe several version of same codec onto your system , such 32bit version and 64bit version xvid codecs ,it may cause this issue  too .