This instructable will teach you how to use this unsupported feature and a variety of hardware and software modifications to use TWO keyboards and TWO mice on one computer. So, the good men and women at Valve kept it in the code for the PC version too.
It was implemented on the Xbox 360 version of the game. Background: Left 4 Dead has had an unsupported feature from the very first demo that allows individuals to play with two players on one PC.
Love L4D? Want to play on one PC with 2 players, 2 keyboards and 2 mice? Then follow me, to freedom from the controller.
