Use a keyboard remap appication. I have used the second and third of these apps and they always do a good job in reasigning or refreshing the function of any key or key combination. In you case you would need to refresh the Windows key function or in case of it not taking, create a new combination (Windows Key + ?), and once the new combination is working you can use the app again to reset the normal Windows Key function.
Remap Keyboard Keys with These 3 Free Apps [Windows]
http://www.makeuseof.com/tag/remap-keyboard-free-tools-windows/
In case you need to create a new key combination, check here for existing key and key combination functions so you don't try assigning one that's already in use
Comprehensive list of Windows 8 keyboard...