Thanks for the welcome.
Have done all that already i.e. copy/paste and also re-registered and checked my date and time and it's all bang on. It still tells me that the key is invalid. I can't even get the program as far as 1st boot.
Can you try uninstall / boot / install / boot?
Or, at least, the repair function at Control Panel > Add/Remove programs). I'm not sure you will have this option without a license key.
Did you downgrade from Pro version to Home?