A trial has been done HERE. There is also a good reference found at knowledge base of Macromedia.
A very good tutorial is also found HERE. At Web Studio Forum the moderator has listed codes for various audio and video files you want to play.
The clsid (class id) used for the Windows Media Player appears to be wrong in some examples I found according to this reference at w3schools.
The official guide is here from MSDN.
The major trouble is that Microsoft doesn't really support other browsers other than its own IE. I have just tried that same code works OK in IE but not in FF.
If you are expecting users to use FF to view your website it is important to alert users to check if their FF installations has plugin for WMP installed properly, steps to follow are here in this FORUM.