Divx player Audio Problems, do I need to fix this?

Every time I play a video or link that has a divx player the audio does not play but the video is perfect. I get the message "The file contains a track in unknown format. You may need to install a DirectShow decoder for this audio format in order to hear the soundtrack".

I have VLC media player so I though that would cover all of the codecs for audio and I do not want to install something that may install a virus on to my computer.

I tried downloading one from CNET but this failed to work

Can someone tell me if this is just one of those adverts to download a virus or it is genuine message and that I do need to install this DirectShow decoder. If so then where should I download it from?