Unlike the 2022 reboot (Modern Warfare II), the 2009 classic uses older architecture like DirectX 9, SecuROM (on some physical copies), and a peer-to-peer matchmaking system known as IWNet.

: If you encounter errors, right-click the game in your library, go to Properties > Local Files , and select Verify integrity of game files . 2. Physical Disc Installation Call of Duty®: Modern Warfare® 2 (2009) - Steam

: Find "Call of Duty: Modern Warfare 2 (2009)" on the Steam Store.