Someone should really make a new WMP plugin. There is
WMPlus 2 but it got a known bug with WMP 10: it doesn't work with the
first song you play when you open WMP. You have to click next or stop -> play to make it work.
Now with the new MSN Messenger plugin for WMP when you're using 7.0.0632 it should be no problem at all to create a plugin to show your current song in WMP in a conversation. (and no, I'm not talking about a function like (!WAT) (in a conversation), like Mylo means, not in your name!)