Steam and Valve are again giving away full version pc game for free. This time it is Alien Swarm. It is from the same team that made Left 4 Dead series and Portal 2. It releases July 19 around 10AM PST. It works on Win7, Vista, XP with minimum P4 3Ghz.
Alien Swarm is a tactical, 4 player co-op action game with a top-down perspective based on the brilliant mod of Unreal Tournament 2004. The aim of which is to progress through sci-fi levels killing waves of aliens with a selection from a 40-strong arsenal of weapons, Persistent statistics, unlockables and achievements feature.