Cannot not activate game

[Buzpilot]

your suggestion 1 - I cant even try as I didnt install COD on my disc...thers no exe file I can browse to add as non steam game.....I got one file from getgames which automatically downloaded COD. Then I got install button but once I press that button files unpacked (although that was fast unpacking), asked me to choose language version and after that Accep agreement bla bla bla (I clicked YES), then It opened Steam activation window...then when I typed a key (I received via email) it says its invalid product key. I found a download folder but nowhere COD install file just steam install but when I run it its the same as via file I got from them (and downloaded a game)....pfft

Did you run installer as admin?