It may be possible to do this by using the Prevent Window Deactivation Function in a Window Location rule for Windows Media Center. I'll do some testing here and I'll post an update as soon as I have some more news.

Thanks!

Ok, I've just done some testing, and it looks like all you need to do to get the mouse cursor out of the full screen Windows Media Center window is press Alt+Tab. That will focus another application, allowing you to move the mouse out, while leaving WMC running.

Hope that helps!

No problem! When I tested it, the Windows taskbar does indeed come to the front, but there's not much that can be done there, as there's no way for us to prevent the Windows taskbar from setting itself on top