When I purchased Half-Life 2 I didn't have the option of not installing Steam, and as soon as I lunched the game (which I already entered the serial key for, so I shouldn't have to unlock it in any case) it started updating it. If I didn't have internet connection it wouldn't let me lunch because it wasn't updated. This, to me, means that I cannot play single player HL2 game w/o having an internet connection - that's just twisted.