Ok, I will try to help.
1. Is your copy of Civ IV a purchased version or have you downloaded it?
2. Have you an Anti Virus Tool?
If not: Look at Google for a free Anti Virus Software or a trial version. Check your PC.
If your Civ IV version is an Orgiginal Version, delete it and reinstall it from DVD.
Does it now run with DVD in the drive?
If yes - make a full Image with Alcohol 120! Mount the Image with Daemon 3.47. Start a Tool called SafeDisk 4 Hider (can be found on GCW). Start the tool. Play without DVD . . . .
Greetings, 007