codec issues for file

I ve donwloaded a video file - windows media player says that the it cant play it wrong codec. So i tried VLC player & divx payer and they wont play it either. I've also used the Gspot codec applcaition which says that i have the codec

Ready (219 codecs loaded)

It lists the file as a .rar when it looks like an .avi

It then says
Mime Type : application/x-rar-compressed

Does anyone have any ideas how i can get it to play ?

I'm running vista

thanks