Ouch. I just tried installing a Logic 9 Express upgrade, from my 8 Express. It asked for my 8 serial number, but when I put in the one I had, it said it was an upgrade serial number, and it needed the original serial number. Well, the one I entered is the only one I have or can find. Is there anything at all I can do? And I don't understand why the serial number of the current one on my computer is enough, even if it's "only" the upgrade serial number, cause, wouldn't I have had to prove ownership for the 8 to have been installed?If the system finds an old serial number, it won't ask you for it again. That's why most people only have to enter the upgrade number.
If you install on a fresh system, you enter your Logic 9 serial number. If this is an upgrade number, you will need to enter a serial number for an older full (non-NFR, non-Education) version of Logic! This can be an XSKey with a full license of e.g. Logic Pro 7, but _not_ an upgrade serial number to Logic 8. Older upgrade number become useless if you want to upgrade to the latest version.