One thing that seems to be nice about being a PC gamer is Steam. This weekend Steam is giving a trial period to download and play Modern Warfare 2. It's only the multilayer but it's still free. The free trail started April 8th and will run through April 12th.
This from Steam: "The definitive online experience, Modern Warfare 2 returns with a host of new perks and enhancements. Those who wish to enjoy every moment of the Modern Warfare 2 multiplayer Free Weekend may pre-load Modern Warfare 2 multiplayer now. There is no obligation to participate."