With what plugin do you use it ? What version of Windows MediaPlayer OSD do you use ?For me it isn't working anymore. I use MP1.0 RC1
You can try newer version http://mediaportalwmposd.googlecode.com/files/WindowsMediaPlayerOSDSetupV1.3.0.0.msi . Check configuration of MP, the WindowsMediaPlayerOSD process plugin should be enabled. If it still does not work, it could be a problem with TVgemist, may be it uses different player with this version of MP. Also it could be helpful to see logs.I have to look at home for the version, but my system has been build up this year so I think it is this one:
MEDIAPORTAL - free MediaCenter HTPC Software - Windows MediaPlayer OSD
In the previous version of MP I used it in combination with TVgemist, that let met look to streaming videos. The plug in was able to show the OSD. But nowadays it doesn't.