I recommend ffdshow in the place of xvid and/or divx5 these days. I've personally experienced a lot of problems recently playing things with xvid directshow filters (player lockups, etc) and there's the whole "keeping up with the versions" thing which isn't a fun game to play. ffdshow tends to kinda just resolve that, and will probably resolve your problem as well.

I won't personally recommend winamp as a video player, because .... well ... it just feels wrong to me. You can use whatever, though. As long as it lets ffdshow hook xvid playback for itself, you should be fine.