My situation: I have brought half life 2, and half life 2: ep1 from ebay. (both are pre-owned). I have heard (i haven't got them yet, so i haven't tried, and someone only told me after i had won and payed) that when the game is installed onto one computer, it cannot be installed onto another (something to do with registration number). Thats about all i know. I want to know if i can play these games on my computer (multiplayer as well) and if not, what i can do about it.
Also, the guy who sold me half life 2: ep1 gave me a password and account name, i dont know if this changes anything.
Any help would be greatly appreciated.