second installation of CS:S

[Che]

hi all,

I the collectors box from HL2 with CS source etc.
Now I want to play CS:S on a second PC.

I think to recall that CS:S was free to dowload if you have a HL2 key, but not sure about this.
I ask this because I can buy CS:S or a HL2 (without CS) game and the price of the last is quite lower.

Any ideas/help?

thanks in advance.