I don't think there is any way of telling but suggest you
phone the activation people. If anyone knows, they should.
http://www.adobe.com/activation/phonenumbers.html
You can install RH7 on a machine with X5 but you will have
issues if you need to use RoboHelp for Word in X5. Importing Word
docs and printed documentation will still be OK.
Help others by clicking Correct Answer if the question is answered. Found the answer elsewhere? Share it here. "Upvote" is for useful posts.