Paul wrote:

"Software as a service". Um, OK. Gotcha.

I'm not quite sure exactly what happened, but I think this was the
sequence.

1. I had Windows 10 Pro set up to never update.
2. Windows 10 Pro was just fine, stuck at Version 1511 OS Build 10586.1106
3. All subsequent updates failed, but automatically backed themselves out
4. The 16299 Upgrade from Nov 2017 failed in Jan, but didn't back itself
out

Anyway, the hard drive and memory were checked out by Microsoft so there's
nothing wrong but the bricked operating system, which is no big deal since
I've bought a new terabyte disk, and now have two terabyte disks side by
side (which I might RAID once I clean them out - but I never did RAID
before and googling finds that there are a LOT of up-front decisions to
make).