If you are using a 32-bit version of Windows, navigate to the following registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Activision\Call of Duty 4 Go to the 'Start' menu, select 'Run', type 'regedit' and click 'OK'. If it still does not work, please try deleting your Call of Duty 4 registry entry: NOTE: The CD Key for this title is not shown to the user in Steam. Verifying the GCF Cache solves most CD Key issues for most users. If you are running in Windows XP, take the following steps:Ģ) Go to the 'Start' menu, select 'Run', type 'regedit' and click 'OK'.ģ) Navigate to the following registry key: HKEY_CURRENT_USER\SOFTWARE\VALVEĥ) Check the boxes for 'Admin' and 'System' to 'Full control' and 'Read'.įirst, verify the GCF Cache for the game: If you are running in Windows Vista or Windows 7, please completely exit Steam, and right-click on the shortcut which you use to launch Steam and select 'Run as Administrator.'

If you are having difficulty accessing the multiplayer portion of the game due to a key error, please take the follwing steps: