ok, first of all... sorry for my bad english
Xion can not be the default player. Windows does not recognize it as you can see in the picture below: clic here!
This causes me problems using a Microsoft keyboard (Natural Ergonomic 4000) that has buttons for Play/Pause. I press it and open the Windows Media Player instead to pause the track Xion
All this on Windows 7 x64
Hopefully they can solve this