Firefox video plug in not installing

[TallTravel]

OK, I really like Firefox, and use it most all the time. The only exception is when I want to watch movie videos on Yahoo.com (generally previews), news video broadcasts, and sports videos and replays.

Most times the result of my bringing up one of these online videos is:

Yahoo Movies
Click here to download plug in

At the top of this screen is a green clover and a menu which tells me:

Additional plug ins are required to display all the media on this page.

So I click on Install missing plug ins on the top right of this window. The system searches the net for plug ins, and the plug in finder service shows up and begins a search.

Result is Completing the plug in finder service, which also says no suitable plug ins were found. Unkown plug in (application/x-mplayer2)

I have tried this 100 times, and it never finds the plug in it wants. As a result I have to switch back to IE to see the video. Some videos play in Firefox, others don't.
As you might guess, these same videos work perfectly on IE 7.0, every time. I have MS Media Player installed, and it is usually the choice for media.

Any specific suggestions?

Windows XP Media Center with 2 GB RAM. Firefox 2.0.0.3

[chuck4456]

Go to FIREFOX ADD-ONS/PLUG INS from your TOOLS option. Install what you don't already have. They offer FLASH PLAYER, SHOCKWAVE, etc. I did that. My YAHOO vids in Firefox all work.