As explained many times on the forum, the installation of a scenery doesn't have anything to do with its activation. And rightly so: it would be VERY annoying if you had to reactivate each time you wanted to uninstall/reinstall the scenery, or even if you uninstalled FSX.
The activation is stored in your Windows registry, so unless you change major hardware components, or reinstall Windows from scratch, your activation will stay. And no, changing the simulator folder won't have ANY effect on the activation, unless you also changed the hard drive Windows boots from in the process.
The reason why you have a reactivation prompt, is because you have a Serial Number for KIAH in your registry, which is odd since, according to your report, "you had the demo". If you haven't purchased the scenery, you are not supposed to have a serial number for it in the registry, since the software won't store a serial number until it has been successfully activated, which can obviously happen only if you purchased the product.
Since I cannot find any orders from KIAH from the email you are using on the forum (although I see other orders from that address), it really seems you never purchased it so, it's not normal you have a serial number for KIAH in your registry.
Is that serial belonging to you ? Have you placed it manually ?
It's best if you contact us by email, because we cannot obviously discuss about serial numbers in the forum.