do the below:
install the most recent version of DirectX 9c from
Microsoft
then do the following for a clean reinstall:
Uninstall and Reinstall Civ4
Delete \Program Files\Firaxis Games\Sid Meier's Civilization 4\
Delete "...\documents and settings\<username>\my documents\my games\sid meier's civilization 4"
Delete "...\documents and settings\<username>\application data\my games\sid meier's civilization 4"
(note: application data is a hidden directory so you need to configure windows explorer to show hidden files, also these directories in application data are sometimes removed by the uninstall routine)
Delete "...\Program Files\InstallShield Installation Information\{CFBCE791-2D53-4FCE-B3FB-D6E01F4112E8}"
(note: InstallShield Installation Information is a hidden directory so you need to configure windows explorer to show hidden files).
Restart the computer.
Install Civ4, immediately patch it to 1.61 (download it fresh from
here)
then install the 1.74 patch (from the downloads database here)