help with avi codecs

hi, can someone help me....
im having trouble with avi files playing them in windows media player.....
it comes up the message:
“windows media cannot play the file.One or more codecs required to play the file could not be found”
I am using xp professional 2002 service pack 1 with the latest version of windows media player version 10.00.00 3646.
I have set the media player to update the codecs required daily from the web.....
so how does one fix this problem????
does any one have any suggestions?
thanks..
jezza....

The option to automatically download codecs in Windows Media Player has one inconvenience: it will only download Microsoft codecs. For non-Microsoft codecs you have to find the codec and install it manually.
In your case since you don’t know which codec you need you should probably use one (or more if the one fails) of the diagnostic tools on this page
http://www.moviecodec.com/questions/neededcodec.html

thanks for your reply,
yes i understand microsoft wmp does this.....
what is the best diagnostic tool you can personally recommend?

I personally like gspot and avicodec, but videotoolbox is useful when I want to find a matroska file’s codec.