Audio codec missing

I’m downloading a film from Kazaa.It’s a DVD Rip
xvid-vite avi.When I try to preview it with Windows Media or Divx player,I get a great picture but no sound.Both wm and Divx say I’m a codec missing.Can anyone suggest which one I need,and how to get it?.I already have the DIVX 511 bundle of codecs.Picture fine no sound HELP!!!!!!!!!.Thanks a lot.

Read through a few of the posts in this section:
http://www.moviecodec.com/board/3.html

Thanks a lot Frightfoo,I’m not very clued up on
all this technical stuff,but I did as you said
and EVENTUALLY found somewhere to download the AC3 filter and BINGO!!!!! it worked.
Thanks a lot for taking the time to help me my friend,you’re a star,
Have a lovely Xmas and a Happy New Year.
Ronnie.