It doesn't matter how much software exists or is in use. We are talking about portability here. For. Net it is is not an issue at all and for Win32 C/c++ only a recompile is necessary. Oracle DB exists for Windows IA64 and office does for Arm. Those are proofs that like any other sane platform portability is not a big issue for Windows.

I think you don't have any idea how much it costs to port a major application like that.

Even if everything goes smoothly with the codebase, just setting up another build environment for something like ARM means installing a new compiler version and toolset. Many (or most) dev shops are stuck on 6-10 year old compilers.

You also multiply the QA regression cycle costs by some incremental factor.

There are lots of applications small and large, that to this day, don't even ship a 64-bit build.

Yes, there are some applications that have been ported. Even if you were to come up with a not-short list of them I would submit everything else in the world that has not.

I think you are confused as to what exactly we are debating here. Porting costs are real - somehow Mac software isn't magically a free port to ARM. The porting costs depend on code base, complexity, various other things. That's however not what we were debating - the debate was Microsoft has never done it and so it might be hard for them. The counter point I was making was Microsoft has been there and done that and there is no reason to believe Windows software is any harder to port to another platform than Mac Software except for the scale part - Windows just has a ton of more complicated software than Mac has had and porting "toy" Mac apps will be less of an effort than say porting a big Enterprise Windows app. However it isn't fundamentally easier or harder.