So, I did something dumb and tried moving the address book from my Lion installer over to my iBook G4 running 10.5.8, and it "installed"...sort of. It replaced the Leopard Address Book, but then when I opened it, it wouldn't run. Yes, I realize how dumb this was. So, then I deleted the app. So, my question is this. Am I able to copy the app from my iMac G5 and reinstall it on my iBook G4? Thanks in advance for any assistance/guidance. And please don't reply with critical remarks when I have already shown how stupid I know that action was.