To play Call of Duty 2 you will need a minimum CPU equivalent to an Intel Core 2 Duo E8400. The cheapest graphics card you can play it on is an NVIDIA GeForce 510. The minimum memory requirement for Call of Duty 2 is 4 GB of RAM installed in your computer.
An Intel Core i5-2500 CPU is required at a minimum to run Call of Duty: Modern Warfare. However, the developers recommend a CPU greater or equal to an Intel Core i7-6700 to play the game. Provided that you have at least an AMD Radeon R9 380 graphics card you can play the game.