I have seen several people asking about this and no real definitive answer and the wiki directions are kinda vague. Here is how I do it. I have a boot drive and then a games drive.

Step 1: Make two new folders on the root of the drive (in my case I used D:).
D:\maps
D:\images

Step 2: Copy the compass_map_mapname.iwi and loadscreen_map_mapname.iwi from COD4\raw\images diretory to D:\images.

Step 3: Copy the mapname.csv from COD4\raw\maps directory to D:\maps.

Step 4: Open Winzip. Click on new zip file. Name your zipfile and place on the root drive. Example: mapname.zip saved to D:\

Step 5: Click the add files button and select the two .iwi's from the images folder you created. ****Make sure you have the checkbox for Save Full Path is checked****

Step 6: Click the add files button and select the .csv file from the maps folder your created. ****Make sure you have the checkbox for Save Full Path is checked****

Step 7: As you added the files it created the mapname.zip file. Open a DOS window and navigate to the root directory. (In my case D:) List your directory and you should see the mapname.zip file there.

Step 8: Type rename mapname.zip mapname.iwd

Step 9: If you are setting up the server make sure the mapname.iwd is copied to the COD4\Mods\whatever. Whatever is the mod your server is running whether it be Modwarfare or AWE4 or whatever.

I hope this helps some people. I know I had to stuggle with it to get through and finally get it all figured out.