Ending months of speculation on the matter, Microsoft has revealed that Windows 8 on ARM will indeed contain a desktop—and that desktop versions of Word, Excel, PowerPoint and OneNote will all be pre-installed.
Microsoft insists that the desktop holds real value, and that it makes Windows less valuable to users if it was missing (a view we're sympathetic to). To that end, Windows 8 on ARM ("WOA") will have a desktop, with a taskbar, that includes Explorer, most of the current desktop utilities that ship with Windows (though not all, and Microsoft hasn't said what won't be included), and supports applications. All WOA machines will support USB and Bluetooth mice and keyboards, so users who want to will be able to use the desktop in a traditional way.
To prove the point, the company has produced a video showing the desktop running on an ARM system. The video gives a first look at Office 15, and though we don't see much of it, it appears to be a Metro-esque evolution of Office 2010: it still uses the ribbon, though it's now collapsed by default, and the aesthetic is much flatter and simpler (and so it unfortunately doesn't match the conventional Aero styling of Explorer's ribbon).
Excel 15 on Windows on ARM
But though it looks the same as the traditional desktop, it has one major difference: it won't run any old application. Microsoft has long said that WOA will not include an x86 emulator, so legacy applications would never run directly on the platform, but there was always the possibility that existing desktop applications could be recompiled. That option is now unambiguously eliminated, with Microsoft saying "WOA does not support running, emulating, or porting existing x86/64 desktop apps." Office is a special, unique case. All third-party applications for WOA will be Metro applications delivered via the Windows Store, and must meet the restrictions imposed on those applications.
Word 15 on Windows on 8 ARM
PowerPoint 15 on Windows 8 on ARM
The company said that it will in some way make it very clear to consumers that Windows on ARM is not identical to the x86/x64 version, to avoid the possibility of confused users trying to use x86 software on ARM machines. It stopped short of explaining how it would do this.
Windows on ARM will be restricted in ways that Windows on x86/x64 are not; the non-availability of third-party desktop applications, combined with the UEFI booting restrictions, mean that WOA will be in some regards much closer to the iPad experience than the traditional Windows experience.
As with the UEFI lockdown, the objective here is absolute robustness and appliance-like simplicity: for Microsoft, the risk of opening the platform to spyware, buggy drivers, extension hijacking, and more is too big; these things can be far more ruinous to the user experience than the inability to run any old program that you find on the Internet. The result is almost paradoxical: to give users greater control of their systems—to make them predictable, safe, and secure—Microsoft is taking away some of the control users have of their systems.