>History matters; the Android codebase is designed to be ported in ways Microsoft is probably culturally incapable of even imagining.
NT is portable. It's been ported to at least four CPUs that I know of (x86, Alpha, MIPS, and PowerPC), and MS has announced that they will deliver it on ARM.
I don't much care for MS, but pretending that they're incapable of writing a portable OS is nonsense.