Originally Posted by
SkrilleX.
Option 1: Download the DLC from the downloads page and extract everything from the archive into your MW2 folder. Then download Move_Stimulus, also put it in your MW2 folder and run it. Now you should be able to play, if not, move down to option 2 below.
Option 2: On Vista/Windows 7: Open the Network and Sharing Center window, click Change Adapter Settings on the left menu and disable any adapters you are not using. Only leave the adapter you are currently using for your internet connection enabled. Now run the game again and if it still doesn't work, make sure you have the DLC by following option 1 above. If you are sure you have the DLC, move down to Option 3 below.
Option 3: Open Device Manager (Windows key+R > devmgmt.msc). Find your network adapter. Uninstall the drivers. If your PC needs to restart, do so. If not, use Device Manager to let Windows reinstall the adapter's drivers again. Confirm that your internet works after the installation finishes and run MW2.