This is Counter-Strike Condition Zero, playable offline or through Virtual LAN such as Hamachi.
Just get hamachi through all computers that want to be connected, and then create and join the same network. Please see hamachi help for more details
Then when ingame, one person creates a game, and all the rest in the network go to console and type "slist" and it should show the game up the game with the IP adress with other details. if it's the only server there, type "connect 1" and it should connect.