Can't install because Steam is 'temporarily unavailable'

I just got a new laptop and I'm trying to install my existing version of Civ V and mods from DVD. I get the message 'Steam is temporarily unavailable' There's an old thread about this issue, with links to instructions on how to fix it (http://forums.civfanatics.com/showthread.php?t=391164), but all the links are dead. Does anyone know how to fix this?

If you already have the game from a previous computer, forget about the DVD. Just install steam from Steam's website. Steam may send you a four digit code via your e-mail that you gave steam from the previous installation on the other computer. It will then let you reload any of your steam games that you have in your library.

It worked perfectly and I'm up and running. Thanks very much.