Thanks for the reply sranshaft, I hope you had a lovely Christmas.
I don't think I made myself very clear in my post - I had discovered how to toggle the window but could not attach the 'viewer' overlay that shows any visualisations, while music is playing, or video. When you show the viewer, it does not appear as a DX object on the Object navigator and can, therefore, not have a name that you can place in the script.
I think the problem may be that it is generated by Windows Media Player and not DesktopX.
I might try something else...