If you are reinstalling them on a new computer that might be difficult. I know impulse did have some method where you could burn the activated game onto a DVD or something and install that way, but who knows if Gamestop has continued to support that feature, and I never had to use it anyways.
If at all possible I think the easiest thing to do would be to temporarily hook up your PC to the internet, perhaps by borrowing a friend's laptop and forming a LAN and using the share internet feature through that.
