Why Microsoft should, and shouldn't, support legacy Windows desktop on ARM

Ever since Microsoft first announced that Windows 8 would be compatible with certain ARM system-on-chip processors, questions about what this would mean for existing Windows applications have been abundant. ARM's strength is in low-power applications, and the decision to support the architecture was plainly motivated by the needs of the tablet market—which left observers wondering just how much of Windows would actually be supported on ARM? Just the bits relevant to tablet and consumer applications, or the whole shebang?

When Microsoft revealed and then described Windows 8's Metro-style tablet interface, the company left the ARM questions unresolved. Windows 8 has two distinct kinds of application: traditional Windows applications that run on the desktop, and new finger-friendly Metro-style applications, with the latter integrated into the new Start screen, and the former segregated off into a separate desktop. This led to speculation that ARM Windows might support only Metro-style programs, and exclude the desktop altogether.