Microsoft has Windows running on Arm already

Wintel alliance sobs into its beer and remembers the good old days
While departing from the x86 obessessed world, it would give Microsoft access to machines running Qualcomm Snapdragons, Apple A5s and Samsung Hummingbirds. The cosy relationship between Microsoft and x86 architecture, which lead to the successful Wintel alliance, is starting to cost Microsoft.
X86 does not work well on mobile gadgets because of its high power draws and inefficient cooling. However the demonstration of Windows running on an Arm chip at the MIX Developer Conference in sunny Las Vegas, shows that Microsoft is serious about getting its software onto as many devices as possible and it does not care if it upsets Intel in the process.