Civ4 is being a little ******** right now.
I'm trying to install it onto my new computer but for some reason it just isn't working. I suspect it may be a hardware thing because it worked just fine on my old laptop which ran Windows 7 - same as my new desktop.
If anyone has any ideas, I have a thread in the Civ4 tech support forum.
http://forums.civfanatics.com/showthread.php?p=14381934#post14381934
I was able to get around a similar refusal to work issue with Rome Total War because Steam would accept CD keys but I don't believe Civ4 ever came with CD keys. If it did, the manual doesn't mention the CD key and the box is long gone into the trash can, probably 10 years ago in fact.