Hi Tomaz1994, You get this error code if there is a problem with the audio device on the computer. Follow the steps below: • Go to Start then Control Panel • Double click on the Sound Tool • Click on the Recording tab • Right click and select 'View Disabled Devices' • Enable the Stereo Mix Now check if you are able to play the game without any issues or not. If the issue still persists, you may try the steps below and check as well. Open the Games folder from the location: C: Program Files Activision Call of Duty 4 - Modern Warfare. Rename mssmp3.asi to mssmp3.bak I would also suggest that you try updating the drivers for the sound card on the computer and check. Refer the link to update the drivers: Update a driver for hardware that isn't working properly: Thanks and Regards: Swathi B - Microsoft Support. Visit our and let us know what you think.