Retail cd and for steam?

[killer916]

I was wondering if I could buy Half-life 2 retail for backup purposes. Since I already have it on steam, could I use it to install the gcfs and use my regular account on steam to play it without cd? If so would it ask for my cd since I have the steam account with HL2 already enabled? Just wondering if it was possible or not.

 

[icspeedracer]

couldn't you just use the backup tool for steam downloaders that people talk about on the thread here?