If you want a Windows flight planner - give Command Flight Planner a whirl (www.commandsoftware.com.au). Its now owned by the folks behind AvPlan EFB (me). Real soon now you can do all your planning on your windows machine then wirelessly push your plans to your iPad/iPhone or Android tablet (and THEN wirelessly push your plan to your panel (Dynon SkyView or Avidyne IFD). Pretty cool!
There are no certified providers doing an EFB for Windows as yet (and AirNav isn't a certified provider). To be an EFB the screen size needs to be greater than 200mm, which rules out all windows phones to my knowledge.
There are some smaller windows tablets out there, but you're spending just as much as an iPad or a decent Android tablet.