i bought a original copy of half life 2 , the game was working fine till in the 2nd chapter or somewhere i came into a big container kinda thing in which there was a person and an alien(something like that) and then i got stuck their..so ireffered to a walkthrough and came to know that the man was supposed to talk abd help me out !!!but in the game the man has no movememnts (even if i shoot at him nothin happens)) so i uninstalled the game .. after some time i again installed it and when i reached the place agan the man helped out ... later again in 3 or 4th chapter i came to a place where there was a man on a small scafolding thing(a little high place ).. there to the man now does not say anything or help me !!! am i stuck ?? and if yes why soo plzz if any one has completed the game tell me!!!