Thanks for the help Dave, but... its created even more problems. On the reinstall I now get this message.
Feature Transfer Error
Feature: Default Feature
Component: Civ4Component
File: D:\Data2.cab
Error: Data Error (cyclic redundancy check).
This is after about 1/4 of the install, on the file C:\Firaxis Games\Sid Meier's Civilization IV\Assets\Art0.FPK
I hope this can be fixed because otherwise I can't play civ at all.