Call of Duty fans who pre-order the PC version of Modern Warfare 3 - either through Steam or Activision's Digital Shop - will also recieve a free copy of the original Modern Warfare as well.
So how it works is, when you pre-order Modern Warfare 3, your copy of Modern Warfare will immediately start downloading. Players won't even have to wait for Modern Warfare 3's release; they can immediately play their free copy of Modern Warfare.
Modern Warfare 3 will be coming to PC in November. Although, this sounds an awful lot like the Ubisoft's deal with Assassin's Creed: Revelations. Perhaps this is a new trend with pre-ordering deals. Would you rather get the first game as well with your order or would you rather memorabelia/DLC?