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Call of Duty 4: Modern Warfare

Support for Call of Duty 4: Modern Warfare:


The community is also a great place to check out. Try these places for help from other users:


Please review the Third-Party Game Support topic to determine whether your question should be directed to the game developer or to Steam Support. Sending a support request to the wrong party may result in a delay in processing your request.


Retail CD-Keys for this game cannot be registered through Steam. If you wish to create a shortcut to this game under your Library, instructions can be found here:

Adding non-Steam games to your Library


Common Errors

Listed below are some of the errors you may experience while trying to launch Call of Duty 4.


Every attempt to launch multiplayer results in the game crashing and an error message stating "iw3mp.exe stop functioning".

According to Activision, this error primarily affects Windows Vista machines. Below are two solutions from Activision and Infinity Ward, respectively:

  1. Activision FAQ for users with a RealTek sound card.

  2. Some users with Athlon XP processors are running into issues with the latest Miles sound file being incompatible. You may still be able to play the game by copying the following file into your Miles directory and replacing the newer mssmp3.asi with the following older mssmp3.asi used in older games such as Call of Duty 2.


    Note: Please only overwrite this file if you are using the XP version of the Athlon processor. This does not apply to the 64-bit version.

    Extract this mssmp3.asi file to the following folder:

    C:\Program Files\Steam\steamapps\common\call of duty 4\miles

    You will be prompted that this file already exists and asked if you want to replace it. Choose "overwrite" or "replace".


ERROR: Could not find zone 'c:\program files\steam\steamapps\common\call of duty 4\zone\english\code_post_gfx.ff'

Please follow these directions:

  1. Log out and exit Steam
  2. Navigate to the "C:\Program Files\Steam\steamapps\common\call of duty 4\zone\english" folder and see if there are any files there. If not, then delete this folder. After you have finished deleting the folder, please launch Steam and move on to step 4
  3. If there are files there, please close that folder and launch Steam
  4. After Steam has started, check to see if it is performing an update on Call of Duty 4. If it does not update, switch the Steam Interface Language to a different language (any language will do). This can be done by going to "Settings" and then the "Interface" tab
  5. Restart Steam when prompted
  6. Call of Duty 4 will begin downloading files. Complete the "Downloading..." and "Updating..." steps until the game is 100% ready
  7. Switch the language back to your language of choice. Restart Steam when prompted
  8. Call of Duty will update. Please allow the game to fully update and then you will be able to launch it


Error: couldn't load fileSysCheck.cfg. Make sure Call of Duty is run from the same folder.

This error happens when you attempt to launch the game without all of the content downloaded. If you are receiving this error and Steam reports that the game's status as "Ready to Play," try validating your game cache files.

Right click Call of Duty 4: Modern Warfare > Click Properties > Click "Local Files" tab > Click "Verify Integrity of game cache"

Once the verification is complete Steam may download missing game content. When it reports 100% again you should be able to play.


My multiplayer rank was reset after a game update

Customers have reported that their Call of Duty 4 mutliplayer rank was reset after a game update on Steam. To prevent this from occurring, back up your multiplayer rank data file mpdata that is located in the following directory:

C:\Program Files\Steam\steamapps\common\call of duty 4\players\profiles\( Player Name )\

If your rank is reset, restore the backup file by copying it to the directory mentioned above and overwrite the file there.



Please see the PunkBuster FAQ for more information.


Steam Forums for Call of Duty

Steam Forums


Contact Activision Support

Contact Activision


Problem with this game?

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Problem with Steam?

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