Got the codex, what's next?

[good-vibes]

I've downloaded an Xvid codex. I now have a encoder and a decoder option in my programs. When I play the video it is like the real player/windows media did not learn that I have the codex.

What must I do next?

[dukenukem]

Install the codec,double click the exe file.Also get g-spot to see if there's a conflict.