I am Reinstalling PShop CS4 Extended to a new computer (old one died). Have box with orig. serial number, but it is rejected during 1st run after installation ran OK. Adobe-CHAT confirmed it was a valid SN for PShop Extended, but they can't help with "Extended". Said I should post to Forums.
Searching, found another forum thread that says:
"As I understand it, there's one download for CS4 Standalone.