However, on startup I still get a prompt that says they are installed and wants to know if I want to activate them.
That prompt doesn't have anything to do with the scenery installation status in the sim or the Scenery Library. It's only related to the Serial Number in the registry, since that is never removed by uninstalling, for the obvious reason that this way, you can uninstall/reinstall an unlimited number of times on the same system, without worrying about reactivating.
However, there's something not entirely clear in your report:
- The question DOES NOT come just because you uninstalled the scenery. The question ONLY comes if you have a Serial Number in the registry which you haven't activated yet, this can happen ONLY in one of those 2 cases:
1) You reinstalled the system from a backup, and used the backup .REG key to insert the Serial Number in the registry, but haven't activated it yet.
OR
2) If you haven't done #1, then some *external* product have added a Serial Number in the registry, because we DO NOT store the Serial Number in the registry, unless *after* it has passed a successful activation.
Do you recall doing any of this ? In any case, to remove a Serial Number from the registry, assuming you don't want to use the scenery in that system anymore, the correct procedure is to choose DEACTIVATE from the Addon Manager. This will reclaim an activation that you can use to reinstall on a new system.
If, instead, the reason for wanting to uninstall was just to clean up your installation (not required if you updated P3D, if this was the reason of the uninstall) reinstall for any other reason, on the same system, you shouldn't Deactivate and, instead, just confirm the activation so, the scenery will be active as soon as you'll reinstall it.