If you see a screen asking for a "CD Key" on the original COD4, hit Cancel . You don't need it anymore. Just set your name and join a server.

So, how do you get an "account" today? It depends on you are using.

Enjoy the game!

If you want to play Call of Duty 4: Modern Warfare online, you might be confused. The original game is old (released in 2007), and its old "GameSpy" account system was shut down years ago.