At present I know of only two devices that uses the Microsoft Mobile Explorer, and that's the Benefon Q and Sony CMD-Z5. However, the information available on the Sony site looks to be nothing more than a flash presentation. Maybe they don't want developers to develop applications that work on their phone?
  
Anyway, Benefon is much better at supporting developers, so go to their developers section instead.
 
The Microsoft Mobile Explorer with skins for the Benefon Q is available after registering as a developer at the Benefon site.