Things You'll Need
Instructions
Open an Internet browser and go to the MapModnews.com website. Click on the "Search on Website" link in the top header. Type "CoD 4 mod: Alien mod" into the search field and click "Search." Open the link and download the mod.
Save the zip folder on your desktop. Find a free extractor program like 7-Zip (see Resources). Return to the saved zip folder and extract the files.
Copy the extracted content by holding "Ctrl" and "C." Open the "Call of Duty 4" program folder and open the "Mods" folder. Paste the extracted content inside by holding "Ctrl" and "V."
Start a game of "Call of Duty 4: Modern Warfare." Click on "Mods" to view all the available mods. Select the "Aliens" mod.