Yes you need a Steam account. Do you mean you are going to buy the retail version? If so I think it is the same as HL2. Once you registered it via a Steam account you can then play it in "offline mode". If you have a credit card/internet and want to pay for it online then DL the Steam client and install it. Set up your account and then pay and DL it via Steam. Saves going to the shops, lol. http://www.steampowered.com/index.php?area=getsteamnow
