Plug-in problem

My WMP11 is not working, instead comes up WMP9, and video is bad.
I notice, in my "about plug-ins", that the Mozilla plug-in npnul32.dll is not abled.Could this the problem?, if this is the problem, how I enable the Mozilla plugin?
I check the plug-ins in the folder and they looked OK.
I will appreciate your help.
Thanks.