I am looking for a way to interact with a standalone full version of Windows Media Player.
Mostly I need to know the Path of the currently played track.
The iTun
The best info I have seen on interacting with Windows Media Player is this article written by Stephen Toub.
He lists a whole load of different ways to play dvr-ms files (doesn't really matter what format they are for this though). The bit that is possibly of interest to you is about using a Media Player ActiveX Control, which you can add to the visual Studio toolbox by right-clicking and adding the Windows Media Player ActiveX COM Control. You can then embed the player into your app, and access various properties of Media Player, like the url:
WMPplayer.URL = stringPathToFile;
This solution is possibly not what you want because it's starting a new instance of Media Player (as far as I know), however it might point you in the right direction.