If you pre-order the PC version of Call of Duty: Modern Warfare 3 you get the PC version of Call of Duty 4: Modern Warfare free.
More specifically, if you pre-order Modern Warfare 3 for PC as a download, you'll get Modern Warfare free.
The influential COD4 launched in November 2007, and kickstarted the first-person shooter's march towards world domination.
Eurogamer's Call of Duty 4: Modern Warfare review fired a 9/10.
"Even without the vastly impressive multiplayer elements, Modern Warfare would be worth buying for its outstanding single-player campaign," wrote reviewer Kristan Reed.
"It succeeds not only for being consistently spectacular, but for the way it has been crafted into something that keeps you engaged right to the very end."