Windows Live Messenger sometimes doesn’t show the music you play on Windows Media Player even though you set it to show.
The work around is the following…
Open up Windows Media Player, and go to Tools => Options (You might need to hit the ALT key to see the hidden menu)
Click the Plug-ins tab, then on the Category Column, Click on Background and make sure Windows Live Messenger Music Plug-in is ticked. If not, tick it and Apply then OK.
See the following screenshot for more info…
Now you should be able to Show what you play on Windows Media Player.