Can someone tell me why, when I have already downloaded Xvid with codec from the official XVID site, a message comes up when I want to watch a video stating 'to watch this film download codec or xvid codec'.

I come across this quite a few times and I am baffled by it.
Hi Wayne H, could you be more explicit please, as I don't know what you mean. When I download something from a site I understood everything would be there that I wanted, is there something else I should have done.


If so, please let me know.