IMPORTANT NOTE: Upon installing the 1.5 patch, you may be prompted to re-enter your CD key. Please be sure to have your Call of Duty™ CD key handy.
INVALID INSTALLATION MESSAGE: If you get a "Setup did not detect a valid Call of Duty™ CD Key" error message when installing the 1.5 patch, you can try one of two things to address this issue:
1. Exit out of the patch setup and load up Call of Duty™ Multiplayer. In the Multiplayer Options screen, re-enter your Call of Duty™ CD key, exit the program, and then apply the patch again.
2. If you get the error again, exit out of the 1.5 patch installer. Completely uninstall Call of Duty™, reinstall the game, and then apply the patch.
Either one of these solutions should correct the problem.