FYI:
_ DC++/DC stand for Direct Connect, a P2P client program. I myself got the horse into using this freeware and now he has become a DC evangelist too
http://www.neo-modus.com for the original DC website
http://www.wewp.com/platform/dc/756/ for the alternate one, but learn that lots of hubs admins hate DC++ and can ban you so be careful.
_ Back to the codecs problem: there's a wonderful, amazing, fantastic (etc...) freeware called.. ahem...
GSpot. No, it's not about XXX movies at all! It's an utility that scans, and look at an AVI file deep deep deep inside (

) to tell you whhich codec was used to encode it. There's a video codec window and a sound codec one. It'll even tell you whether the a^ppropriate codec is installed on your machine! Great isn't it, plus it's free. It's one of the must-have divx tool. Period.
If only other Gspot were free too
Screenshot of Gspot.
PS: Ah, forgot to tell you, BS Player is told to be the greates player ever, even better than divx playa. Plus, it can play subtitle (.srt for instance)