How do deactivate that notice so it will keep prompting every time I load a flight?
By replying YES, of course.
The reason for that question is because you still have your activation key in the registry, because we don't remove it when you uninstall the scenery, and even if you remove the sim, we never remove it. This for the obvious reason so you are free to uninstall the scenery and uninstall the sim, without having to reactivate the scenery "just" because you uninstalled it or uninstalled the sim.
If you don't want to use the scenery on this system, the correct course of action is:
- Let all sceneries activate normally.
- Once they are all active, select the "DEACTIVATE" option in the Addon Manager. This is the option you are supposed to always use when you are not planning to use a scenery on your PC anymore, because in addition to remove the scenery activation from your windows registry, it will also recover its activation, so you won't consume another one when eventually reactivating again, here or on another system.