Some guy did a mod for half life and it had zombies in it. It was really well done. Think the mod was called "They hunger" and it was done by Neill manke (sp?). There are 3 episodes. Maybe the pc game site has all the episodes. I like half life but some of the jumping and timing puzzles could have been left out. Felt more like Super Mario Alien World with guns. Will get HL2, hope it runs on my machine well.