I think current programs like Photoshop are not a problem. How long does it take Adobe to recompile it for ARM? Like a few hours or something (however long it takes to compile for X86).

And how is that CS4 on your shelf going to recompile itself ? But on a more serious note, it does take a LOT more than that. There are plenty of routines in PS that are not only X86, but extension (SSE*, etc) optimized or integrated components from 3rd parties (yes, I worked on a project that hooked into PS pretty deep). Not to mention the fact that ARM is a lot more fragmented (v5 ? v7 ? NEON ? OpenGL (ES) ?) than X86, which is mostly incremental.

Logically, they will want to make use of this shift to implement a 'better' DRM system and they will likely want to make all Windows ARM binaries to be required to be signed and to come from their One AppStore, a la Apple.

<insert 'B-B-B-But, piracy will always live!' comment>

They may even provide ARM binaries for free for current license holders by inputting the product's key into the AppStore; a la Steam.
Now, that would be kinda nice.

This article explains the story of Microsoft Windows and why it is the way it is today http://arstechnica.com/microsoft/gui...dows-sucks.ars Microsoft managed to be backwards compatible with 16bit programs and dos programs by implementing a compatibility a layer for 16 bit and I'm sure Microsoft will implement an x86 compatibility layer on top of the Arm version of Windows, just like Microsoft did with the transition from 16bit to 32bit or 32bit to 64bit.

Of course Microsoft can build an X86 compatibility layer, sort of like they did with the Xbox 360.
But programs will run pretty slow, probably at best 8 times as slow as on a native X86 CPU, so goodbye stuff like Photoshop and 3DMax.

X86 compatibility layer on top of ARM without specific HW support ? Is that a joke ?

I don't think Windows on Arm would be aimed at high end workstations running photoshop or 3dmax, but aimed at small form factor devices such as netbooks.

Exactly. Without the huge application collection windows is just a rather lame window manager with IE.

Windows NT was ported to MIPS, Alpha, PowerPC and Itanium and none of those sold.

Yes but Windows on arm would be for low power devices where most people would just run light weight applications, and also you say it would be a rather lame window manager with ie well that is the point most people are still familiar with the Windows interface and as as long as the Arm version runs Microsoft office then that will be more than most people need.

Well, that's how PC usually were back in the days Microsoft "came".

The question would be whether they are in a position to repeat what they did to the PC market.

I say no. But it will be interesting to watch.