Changing the code in Call of Duty 4 may create problems with the multiplayer part of the video game.While the game is loading, it may not be able to connect with the remote server.It may keep on searching for the master servers without success. Multiplayer on Call of Duty 4 requires a stable internet connection. If there are issues, the internet connection should be checked. Care should be taken when changing the code in Call of Duty 4 in the reg file of Call of Duty. It has to be opened in Notepad and saved carefully to avoid problems.
I have Call of Duty 4 and it runs fine in single player mode, but not in multiplayer. When attempting to join a server in multiplayer mode it cannot connect. A message appears saying the game is looking for a server but nothing happens.
You can change your code key in the reg file of your game:
Open it with notepad and at the bottom you'll see code key (20 characters- number and letters)