Keirannk

Hope you guys can give me an answer. Firs off i live in Northern Canada and Bandwidth is very limited and once you go over the price is ALOT, so i was wonder if i buy ArmA 2 and ArmA 2 OA on Steam can i take this files from his computer and transfer them onto mine but change Serial key or CD-Key and be able to play? or do i have to download the game from steam? Thanks!