Question about activation

[DEATH eVADER]

So I don't have my copy of HL2 yet, the earliset time I'll be able to buy it is friday.

As I don't have a modem and anti-virus software yet, I was wondering, can you activate the copy anywhere (work/school etc).

Question is do you have to install the game components onto your computer first, then asks you to register?

or

do you just pop the CD/DVD into the drive, go to steam. Steam gives you a unique code that you have to remember everytime you reinstall the game?

 

[Edcrab]

The verification process might require you to activate HL2 with a full installation.

I thought that you could just enter the CD key, thus permanently registering the game to your account (and letting your account unlock the game when you log in on the relevant computer), but someone else will have to confirm that.