This is old (2005) information applicable to the original Civ4. If you have patched your game or if you have any of the expansions, or Civ4 Gold/Civ4 Complete, and you are having problems, then your problem is certainly not what this thread was about.
Official Civ4 Patch:
The official 1.52 patch is available for download. Please download and install the patch before trying any other fixes.
This fix has been tried for Inverse Icarus and Unimatrix, and got their games fully working, so everyone give it a try.
You have installed a retail version of Civ4, along with the DirectX update on the CD. You have installed the 5.10 ATI drivers.
1. Download, unzip and run this application.
2. From the menu, select PAK->Unpack.
3. Go to your Civ 4 Folder, Assets subdirectory (CivilizationIV\Assets), select the Art0.FPK file, click Open.
4. You'll be prompted to select an extraction folder, select CivilizationIV\Assets - same folder as above.
5. Wait. The program may appear to hang with the progress bar at 100%, but it will be done with unpacking in 2-5 minutes.
6. Move the Art0.FPK file out of your Assets folder so that Civ4 can't find it.
7. Run Civ4.
Attention Windows 2000 users!!
The Unpak tool doesn't work for Windows 2000, but Firaxis are in the process of updating it to do so. In the meanwhile, you can use the unofficial utility by Gramphos.
Please report your video card and whether this works for you.