Valve is now offering pre-purchase of Call of Duty: Modern Warfare 2 through Steam. They also announce that Infinity Ward's military shooter sequel will ship with Steamworks, and here's a bit on that:

All PC versions of Call of Duty: Modern Warfare 2 will be powered by Steamworks, providing gamers with auto-updating, anti-cheat technology, Steam Achievements, and the recently introduced Steam Cloud.

"Steamworks will make it possible for us to have a closer connection to our fans, and enable us to support our community much more than ever before," said Robert Bowling, creative strategist, Infinity Ward. "Steam is the hands down leader in offering a community focused experience on PC and the inclusion of Steamworks has allowed us to deliver the most feature-rich PC version to ever come from Infinity Ward, which at the end of the day will mean the most to our fans."

Call of Duty: Modern Warfare 2 for PC will include 50 Steam Achievements, enticing players to train a local militia and be "Back in the Saddle" or infiltrate the snowy mountain side base and earn the "Cold Shoulder." Fans may access the game from any computer. And through Steam Cloud, multiplayer game progress will be stored persistently and travel with the player.