I run 2 computers - one for 'everyday' stuff like work, emails, e-commerce, etc. and the other almost exclusively for FSX. Here's my question - can I buy the NGX using my 'main' computer, get the registration code etc, and then physically install the plane on my FSX rig (the 2 computers are networked to eachother) or does the activation only work on the computer that purchased the product/received the activation code email etc? Many thanks. Toni.

As long as the computer you are installing it on has an internet connection. Doesn't matter where you download it onto.