The newer Windows Media Players are not explicity supported by the RWII's software. My guess is that it won't explicitly support WM Classic as well. You will probably get basic functionality from the remote. This means that buttons like play, pause, stop, prev/next should work. However, you probably won't get anything fancy like being able to seek to a specific position using the remote.
There are an extensive number of third-party plugins available all over the net though. Chances are you might be able to find one that will give you WM Classic support the way you need. The good thing is that you can check this out before even purchasing it just by searching.
I'm using a WM9 plugin right now that adds the ability to seek back and forth 5, 30, or 60 sec. Otherwise, my RWII functionality is limited for WM9. It's a good match if you have ATI's MMC softare. Otherwise, I don't find myself using it too much beyond that and WM9.