Call of Duty: Modern Warfare 2 is a first-person shooter video game developed by Infinity Ward and published by Activision for the Xbox 360 and PlayStation 3 video game consoles and the Microsoft Windows operating system. Officially announced on February 11, 2009, the game was released worldwide on November 10, 2009. It is the sixth installment of the Call of Duty series and the direct sequel to Call of Duty 4: Modern Warfare, continuing the same storyline, with Call of Duty: Modern Warfare 3 set to end the storyline.Go to: http://store.steampowered.com/ and download STEAM client
Click “Install Steam” (from the upper right corner)
Install and start application, login with your Account name and Password (create one if you don’t have).
Please follow these instructions to activate a new retail purchase on Steam:
Launch Steam and log into your Steam account.
Click the Games Menu.
Choose Activate a Product on Steam…
Follow the onscreen instructions to complete the process.
After successful code verification go to the “MY GAMES” tab and start downloading.