You know, I might be thinking of selling my copy sometime, but I'm not sure. Used PC game of course, but I haven't tampered with the CD key at all. And would it matter if it's a CD edition instead of a DVD one?
I have one of the below pictured Civilization 4 Gold Editions still brand new factory sealed if you want it. Comes with the Warlords expansion pack plus some other bonus stuff. Bought it for myself, but I honestly haven't had time to play it. PM me and we can work something out.