However the cost is no worse than the cost in the open source world of jumping on technology decisions that then wind up fading away and dying. And the fragmentation in the open source world makes that more likely.

Yes, in principle you can support open source software yourself. But you'd be amazed at the long term costs of doing so when you are locked in to a platform with diminishing market share.

We had almost reached the point where, notwithstanding any commercial licensing barriers, you could either still run application software natively, or it was so old that you could host a virtual machine containing the old OS within the new one. That's a great situation to be in if you rely on the software, and it's also a very nice situation if you write software, because it basically means that once you've got software that works it works forever. A firm foundation keeps everyone safe.

It's regrettable that under Ballmer and now Nadella they seem to have been pushing hard in IMHO the wrong direction with increasingly rapid updates and more reliance on inherently unstable on-line services, instead of playing to those traditional strengths. This makes Windows just as unlikely a prospect for long term stability as anything from Apple or the Linux world these days.

Personally, all I want is a system that I can buy today to do useful work and reasonably expect to still be doing useful work more than a year or two later. It's disturbingly difficult to find software that meets that apparently simple requirement any more.

Their mainframe family still runs most serious financial platforms around the world, and it is routine to run code written decades ago on the latest generation of hardware.

No, it is not cool. It is not sexy. It is not cheap.

But it is backwards compatible. With a vengeance.