Reading your post I do have doubts about my setup, so I investigated and found the cause of the problem.
1 - Uninstalling and reinstalling PowerDVD10, even cleaning the registry, I finally managed to play the AVI file (DivX), but not WMV.
2 - I had mistakenly configured ffdshow, which is activated with PowerDVD10 was enough to disable it. That way I could also play WMV files
So this problem has been resolved thanks to the confirmation of your report, which prompted me to investigate on my system.
THANKS