Aapje, as I said. WMPlus 2 works fine with WMP10 (I use it myself!). There is one bug which is that it doesn't work with the first song you play.
If you installed wmplus, you should type /xmp in a conversation windows.
If that doens't show anything, make sure the plugin in installed. If it shows "(Windows Media Player is not running)" try to skip to another song in WMP10 or make sure the plugin is runnig. Right click on title bar and do as in the screenshot (srry, have Dutch WMP10)