HalfLife2 question!!!
 

Before you get your panties in a bunch I'm not using "the Official HL2Thread" because it has been locked!!!

I bought the game used, & am not interested in playing online anyway, & I didn't get any literature with it. How do I get to the single player game?
When I try to start the game, after doing the auto update, all I get is the registration dialogue. Is there something I'm missing? Where is the single player?

You have to register online before you play either single player or Multiplayer! You need to go thru the online activation! Buying a used version of HL2 was probably not a good idea.