Windows Media and Mozilla?

[Pablo Coronel]

Hello,
I got a problem trying to see some streaming media in the WMPlayer format,
Mozilla asks me to install the plugin (that is already on my PC).
Anyway I installed the plug-in again but it didn;t solve the problem.
The file type is:
application/x-mplayer2

now my question is:
how can I hack Mozilla to open that kind of files using the windows M 
player already installed in my system?

Thanks