download this little program called 'avicodec'. Simply open the video file in the program and it tells you what audio and video codecs you need to run it, then gives you the appropriate web links to go get the corect ones.
Beware, by installing multiple versions of codecs to handle the same type of file format can cause problems due to conflicts. Best to only have 1 codec per format type, if you then want to use a different one then uninstall the previous one each time.
http://www.videohelp.com/tools?tool=AVIcodec