Done it a few times in the past; every time had to search for the link. Now it's here, much more convenient.
Using Steam launch options to install retail games from disc
Using Steam launch options to install retail games from disc
Log in to Steam and click on Library.
Right-click on the game, select Delete local content, and confirm.
Insert the first disc into your computer.
Close Steam (Steam > Exit).
Press Windows Key + R to open Run
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.
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
