I can't play XviD on BSP.
 

I've downloaded the latest version of BSP through the official site, and I have the latest XviD codec. But my XviD movies won't play. I've also tried ffdshow, but it still doesn't work.

Install this, and let me know if it still doesn't work.

I have exactly the same problem, tried installing that and still got the error message:

Unknown file format (XVID)

Can play anything else without problems, and playing the same file in DivX Player 2.0 plays about 5 seconds of it then stops :(

Media Player just won't play any Xvid files at all.

The decoder Wam7 suggested didn't help. However DefilerPak solved my problem. I can't remember their site URL, but I've uploaded the installer (and a readme) here:

http://www.student.itn.liu.se/~damfi208/defiler/

So basically, what I have now is:

XviD
XviD-Dec
DefilerPak

And it works. However I don't know if the Decoder helped in this case.
And I have not configured the DefilerPak in any way.