If you purchase a hard copy of a game that is available on Steam, you will also enter the disc's product key into Steam, assigning that game permanently to your Steam account. From then on, as far as Steam is concerned, you own The Orange Box, and you can use any game disc as many times as you like to "accelerate" the game installation process by (obviously) bypassing the download process. If that doesn't work, log into your Steam account there and install your games from disc on his computer - then he will have the locked files on his account when he logs in and can buy the Orange Box from the Steam Store to gain access.
However, any updates (and, in the case of The Orange Box, there'll be a lot) will still have to download and install - and he won't be allowed to play Team Fortress 2, for example, until Steam's done.
However, any updates (and, in the case of The Orange Box, there'll be a lot) will still have to download and install - and he won't be allowed to play Team Fortress 2, for example, until Steam's done.