The Microsoft Vista development team recently released a Windows Media Player plug-in designed specifically for Firefox that will help Vista users accustomed to Firefox more consistently use Windows Media Player built-in features.
When you browse a Web page containing the WMP ActiveX controller after the new plug-in is installed, Firefox automatically obtains the new video plug-in required for playback and plays the streaming video content normally.
However, there is still a small conflict between this plug-in and Firefox 2.0.03, you need to install the plug-in for the first time, restart Firefox, and install it again.
(mydrivers.com)