Problem when installing Adobe CS2 on Windows 7?

I just got a new HP Desktop running Windows 7 to replace my old P4 running Windows XP. Now I am trying to put CS2 on to the new computer. The install goes as planned, but when I launch Photoshop, I get this message “Your Photoshop user name, organization, or serial number is missing or invalid…” I tried reinstalling, but I end up with the same. Any idea what is going on?

Thanks!!