I made that "mistake" only AFTER nothing was working, not before! That means something went wrong with the updated addon manager -
That's what I said in my first reply. At THAT time, your FSX.CFG or your SCENERY.CFG might have been corrupted, so the migration process didn't succeed, because it couldn't modify files with a problem.
What about the registration keys?
Your registration is stored in the registry, and nothing will remove it, unless you reinstall Windows. The *backup* .REG files, which have the ONLY function of eventually saving you from *manually* typing a Serial Number when reinstalling from scratch, are still where they always been: in your Home folder (the folder with your name under C:\Users).
What about the "extra" addon folder now sitting in C:\\Program files (x86) ... I, personally cannot see why anyone would want huge scenery files put into a small SSD.
Then why you choose to accept the default location ?
How this is any different compared to any Windows program out there ? They all defaults to C:\\Program files, but every Windows installer out there, while it might defaults to that folder, which is the officially suggested folder for every Windows program, it allows you to CHANGE the suggested folder into any folder you like.
So, the new Addon Manager installer is now behaving exactly like every other Windows installer out there: defaulting to C:\\Program files, but allowing you to install anywhere.
If you didn't wanted to install into C:\\Program files, you should have selected your other drive.
I certainly was not one of the people who begged for that choice.
Your usage case (OS on a small and fast SSD and the flight sim stuff on another drive) is PRECISELY the one that would benefit the most from the new installer method!!
BEFORE, you didn't had any choice but to install into the root of the sim so, for example, if you installed the sim into a fast SSD on C:, ( which would help a lot with startup times and loading times of the default textures ) so, in order to "circumvent" what was a limitation of our installers, and other installers from other developers that also forced you to install into the sim, you installed the *whole* sim to D: , losing the benefit of having at least the sim starting from the fastest drive ( Windows + the bar FSX will surely fit on a 250GB SSD).
The new installer, instead, will let you complete freedom where you can install. Which means also complete freedom of doing mistakes, like accepting the default choice of C:\\Program files, if you didn't wanted to use that folder.
Now, after I locate my registration entries (please tell me where they are), uninstall 14 airports, then re-install them all again, how can I be sure this isn't going to happen again if there is a problem with the FSX config?
One final thought - what is going to happen when FlightBeam incorporate the rest of their airports without the addon manager like they started doing with KMSP?
You will use their new installers, which will likely install into a different location.
Now, after I locate my registration entries (please tell me where they are), uninstall 14 airports, then re-install them all again, how can I be sure this isn't going to happen again if there is a problem with the FSX config?
Please re-read my previous explanation. The "migration" of sceneries is something that is done only ONCE and ONLY if you had sceneries installed using the OLD installers!
If you uninstall everything and reinstall using only new installers, nothing can go wrong in the migration, because no migration will be made in the first place.
Of course, if your Scenery.cfg or FSX.cfg are already corrupted, even a new installation won't fix this, but that's nothing new: even the old installers would have failed on an already-corrupted FSX.CFG or scenery.cfg.
Your FSX.CFG seems to be fine now so, it's possible your migration failed because of a problem of your scenery.cfg instead but ,can't you just TRY as I suggested and THEN report of problems ? If you will still have problems, then we'll have a look at your other .CFG files, and will obviously fix them.
The only thing which is 100% sure: the installer WORKS, if all your affected .CFG files are clean.