Here http://www.theregister.co.uk/2017/03/20 ... ft_on_arm/
is an article that touches on Windows Server on ARM. Note that it only runs on two, very specific, ARM processors, and that those processors have features that the Pi does not. And, of course, Windows Server is not "Windows" as most people think of it any more than Win10IoT (which does run on some, but not all Pis) is not "Windows" as most people think of it.
Really...trying to cram a typical Windows version onto a Pi is a fruitless task. Not just because the hardware doesn't have the correct instruction set to run it, except under simulation, and hardware just isn't up to the task--too slow and too little memory--but because Windows is such a closed system that will nickel and dime you to death if you want to do anything other than run programs written and sold for the platform. With Linux, you automatically get several language processors, and you can add many more, you have access to the tools needed to write any sort of program you choose with nothing standing in your way, and you have access to the hardware to do--fully supported!--physical computing.
I maintain that anyone that can use Windows or Mac can use Linux (the GUIs aren't *that* different, and learning a second, or third, one will be able to more easily adapt to future changes). For the intended purpose of the Pi--kids learning about computers in the most general ways--the very *last* thing one would want is a closed system that requires spending significant funds just to get even a single compiler. Dr. Upton has referred to the "tablet trap" (computational device as a black box). Windows is little better for this purpose.