If you have not added any new airplanes to your Demo yet, then yes you can register your key code for ICE with the same user account.
If you have added any planes or other content to your Demo install then no you can't.
Once you add anything to your Demo then you are counted as an "upgraded" user account.
If you bought a coouple planes for the Demo and you buy ICE, go ahead and create a User Account for ICE and install it. Then send an email to us and ask us to transfer your planes from the Demo account to the ICE account. Just provide your account details and proof of purchase.
Ok thx Jason. I have not yet added any new planes and understand, what u r saying. We got a deal Jason
I will buy via Amazone - and by the way thank You very much for the support.