If you use Winamp it optionally checks what’s playing and posts that to the Mood instead. This overrides the Twitter post but when you pause Winamp it reverts to the Twitter post. Winamp is checked every 5 seconds and when the playing state changes or track changes so it’s more or less instantaneous.
Installation just consists of copying the .exe somewhere and running it. The first time you run it, it will popup the dialog so you can put in your Twitter ID. Once that’s done it will start in the tray so you can add it to your Start menu and forget about it.