The activation is not related on the sim used, it's only related to the PC hardware or the Windows installation. Some examples:
- Installing in FSX, FSX:SE, P3D v1.x and P3D v2.x on the SAME Windows installation, will count as 1 activation
- Installing in FSX on a desktop PC and on another FSX on a notebook, will count as 2 activations
- Installing in FSX on a desktop PC and FSX:SE on a notebook, will count as 2 activations
- Installing under FSX on Windows 7 on a PC and on a separate Windows 10 installation (like a different boot drive) on the SAME PC, will count as 2 activations
- Installing under FSX on a Windows 7 on a PC, and under P3D and FSX:SE on a separate Windows 10 installation, will count as 2 activations.
Basically, it's the hardware OR the Windows installation that counts, not the number or different simulators you use.
If you don't change hardware and don't reinstall Windows, you can Uninstall and Reinstall any FSDT product an UNLIMITED number of times, regardless how in how many sim you perform the uninstall/reinstall (provided they all run under the same Windows install)
If you REMEMBER to use the "Deactivate" function of the Addon Manager menu BEFORE deciding to do a Windows reinstall or an hardware upgrade (or even buy a new PC), you will recover 1 activation, so your running total of 6 won't be affected.
The Deactivate feature will allow you to do INFINITE hardware changes, if you remember to use it. We give you 6 activations, so you might still "forget" it a couple of times, and still have some headroom for hardware changes.