How to install a game without Steam downloading

If you've bought a game on DVD and it has to be validated through Steam, chances are the people who put the DVD together were too lazy to tweak the installation to install from Steam. This happened to me with Fallout: New Vegas. There is an official workaround, UNLESS you have a Mac.

Installing from Disc instead of Steam
I try to install my retail game from the included disc(s), but the game begins downloading through Steam instead. What can be done?

Mac Users:
If you are using a Mac, you will not be able to install from the disc. Please double-click on the game in your Library list to begin downloading and installing the software.

Using Steam launch options to install retail games from disc

1. Log in to Steam and click on Library.
2. Right-click on the game, select Delete local content, and confirm.
3. Insert the first disc into your computer.
4. Close Steam (Steam > Exit).
5. Press Windows Key + R to open Run
6. In the Run window type:
   "C:\Program Files\Steam\Steam.exe" -install E:
   Replace E: with the CD/DVD drive you are installing from if is not correct.
   Replace C:\Program Files\Steam if your Steam installation is not in the default location.
7. Press OK. Steam will launch and ask you to sign in if you do not have your password saved. Your installation should continue from the disc.

Note:
This process is only intended for retail store bought copies of Steam games (ie. Left 4 Dead, Modern Warfare 2). It will not work for backup discs of any Steam games.