I recently purchased Left 4 Dead 2 with a good discount. I can't install it on my desktop computer, because it's very old and I believe it's not able to play this game. So I am planning to install this game on my father's laptop for playing. Just wondering if I get new graphic card and RAM for my computer in future, will I be able to install the same Left 4 Dead 2 on my computer and play it with the same Steam account? Thanks for your help.