Excitement over the news that Windows 8 will be coming in an ARM-powered version for tablets and other low-power devices has been somewhat tempered by the idea that it will be hobbled, restricted to the pretty yet less powerful Metro user interface. Today Microsoft laid those fears to rest somewhat, implying via its MSDN blog that both the X86/x64 and ARM versions would get the old-school desktop mode, familiar to any heavy Windows user. That's great news for anyone who wants a full computing environment in a small package, not the mobile-style interface of the iPad and Android tablets.
This shouldn't be taken as an iron-clad confirmation: the blog post talks about power-saving measures for "both desktop and Metro-style apps", specifically on system on a chip architectures like ARM. That implies, but doesn't guarantee, that traditional desktop programs will still be allowed on ARM-powered Windows 8 machines, presumably using the old Windows 7 and earlier interface. Microsoft still isn't answering questions on the subject.
Even if a desktop mode is included on the ARM version of Windows 8, applications will need to be tweaked and in some cases completely rewritten to run on the architecture. The situation would be somewhat similar to when Apple switched from PowerPC processors to Intel: initially, some apps would work on x86 machines and some on ARM machines, with a little technical wizardry needed to make a program universal. This is in addition to the distinction between normal desktop apps and Metro apps.
It still seems possible that Microsoft will want to focus on low-power (and in most cases low-function) programs for ARM-powered machines. In recent builds of the x86 version of Windows 8, even the good old Start button seems to have been given the boot. Developers can't even work with the ARM build at the moment, though it's expected to arrive sometime this month. ARM Windows devices aren't expected to reach retail shelves until well after the debut of Windows 8 itself.