How can I force Steam to install Call of Duty: Modern Warfare 3 from disk, NOT from web?

Steam will automatically download the game. Here's what you should do:

1. Close Steam .
2. Re-run Autorun.exe (the disk autorun).
3. Choose the "reinstall" option.

Presto... The game installs from the disks.

After struggling with this problem with no prevail whatsoever for months with different games, I finally found the problem: the CD.

Instead, I copied all the files in the retail CDs, Disk1 and Disk2, into a folder then I moved it to the c:/ directory. (could be anywhere else this was just the easiest for me).

I went into Steam into the left corner (which says "Steam") and pressed Backup and Restore games. Pointing the 'backup' to the folder I created worked and now I am installing it.