Codecs????

[abb0]

I have 2 computers networked at home. On one computer (PIII 667, 128RAM, 16MEG nVidia) I have no problems, all is well. On the other computer (AMD800, 128RAM, 8MEGnVidia) I am having problems playing DivX movies. Playa will play but I have sync problems. All other players I get a grey screen with good sound. A couple of movies have a ticking sound when played on The Playa (with picture)but the other players I get good sound but again np picture. I know this is a codec problem but I have installed exactly the same codecs on both computers yet one computer works well and the other doesn't.
Does anybody have any ideas on what could be the problem or have a solution.
Thanks
Abb0