WMP11 Fullscreen Double-Click not working

When I play a video in XP WMP11 and double-click it to enter fullscreen mode nothing happens, the problem was present in WMP10 so I upgraded to WMP11 but the problem still remained, the problem is only associated with avi's or mpg's, wmv files fullscreen on double-click without a problem, double-click to exit fullscreen works fine.

I have been stuck with this problem for a few years now and would like to find a solution if possible, perhaps there's a corrupt registry key or something that can be repaired.

Any help would be greatly appreciated thanks.