Registering/Activating games from different region?

I've already bought GTA4 here in India for a very low price and plan on also purchasing Left 4 Dead for my brother.

On the back of the GTA4 box, it states the game must be activated in India. My laptop cannot run the game, but could I still install the game and activate it? Would it then work perfectly back in the U.S, including online play?

With L4D, my brother wants to play it online via Steam so would I have to just install it and register it here on Steam for it to work back home?

I just want to make sure if I buy a game here, it'll work fine back home, including the online portion. If GTA4 doesn't work, I'm out only $10 but don't want to spend more money if its too hard/impossible to get them to work back home. I just want to be sure.

 

I thought just DVDs and Console games suffered this, I have no idea about region codes for PC games.

 

I don't think there's any code for PC games.They sell European version of PC games here in Quebec along with the NA version when the NA version doesn't support French