Zombie Panic: Source version 1.25b includes stability fixes, a new weapon highlight system, and a few map and model fixes. This file is the full client for Windows clients and dedicated server hosts for version 1.25.
The basic idea of the Zombie Panic is to create solid game play that is based on a classic zombie outbreak scenario, the living dead are coming for the last remaining humans, and these survivors must fight them off and live through the day. v1.2 of the popular Zombie Panic: Source multiplayer mod for Half-Life 2 has been released. This is the full version of the latest Zombie Panic: Source (up to now) so you don't need any previous versions in order to install this.
One of the new awesome features in Zombie Panic: Source is the Carrier Infection, which can infect humans with a 10% chance each hit the carrier makes towards a survivor. You can see when a human is infected, as he / she will turn green in your zombie vision view. You really should let them stay alive, as they will slowly turn in the undead, and can turn against the humans from close!