It was an interesting solution, in the end...
Sure, AES2.38 spat the dummy.
Before getting round to the patched download, I moved some stuff around in the sim, in preparation for some future adventures.
But I did not install any new addons; what I did do, amongst other things, was to copy in a previously installed Algiers scenery from the archive hangar.
When I ran the patched AES, it started to do the usual nanny thing and I go yesyesyes get on with it.
In there, it would have asked if it should activate DAAG.
The DAAG scenery of course has a landclass issue, so well done all of you who are now going: told you so!
The sim is back, and I of course am delighted.
Sorry for the disturbance, and thank you!
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The Postscript:_
The XP Restore function only works on my machine for restore points you created, not system generated ones, like Win Defender updates. So lesson learned.
I have removed WIN updates (even though it growls at me every time the system boots). There is nothing I need from MS on this computer.
I also removed all those other things that know better about how they take over resources on the machine. Hewlett Packard is particularly bad at this.
Java too, is gone, it phones home constantly.
As is iTunes, horrible Know-it-all software.
I ran my Registry repair tool, which fixed 212 orphan Registry entries.
I defragged the drives,sorely needed it turns out.
My WIN XPSP3 computer runs FS9.5 as if it were new.
Probably a Good Thing to have a minor crisis every now and then!
Having done all this: if it were a system problem, be it hardware or software, I really would have walked away.
In fact the entire box would have been junked. There is no way I will configure a new computer or even rebuild FS9 from scratch.