I nearly fell off the cliff. Really - they (Microsoft) shouldn't advertise. [I did eventually upgrade and all is well!]
I am not of course a typical user. Fortunately I had remote software installed so I could operate the now disabled machine from another computer.
Windows 10 not only wants to grab all your data and supply all your apps with its default settings, but it also can't operate some monitors and turns off your operational monitor after a few minutes in such a way that it won't turn on again. Now that's a recipe for being disabled.
I also tried one update on my oracle data and it lost the record. Fortunately it allows you to step backward to Windows 8.1 and there it was, I say with relief, successful. Then I found the corrupt record in my data and have recovered it.
Frankly astonishing that it could be so bad. These are not normal bugs.
Better is a word that is in currency right now. Take care, the better is the enemy of the good and may indeed be worse.