Namdoc:Note to Steam Users

The version of SimCity 4 sold on Valve's Steam service is Version 1.1.641, and fully compatible with the Network Addon Mod. However, there is one small tweak that the NAM Team recommends for all Steam users to make when running the game with the NAM. The default shortcut key in the Steam Client for the Overlay Display is Shift-TAB, which is also the same key that SimCity 4 uses to cycle backward through TAB-based menus, including virtually all in-game NAM menus. It is highly recommended that Steam users change this shortcut key when using the NAM, or disable the Steam Overlay entirely.

To change the Overlay Shortcut Key, while in the Steam Client, go to View > Settings > In-Game, and click on the "Overlay shortcut key" box. Input an alternate combination of keys while the box is selected, and once the contents of the box have changed to match your new shortcut, click "OK" to save the settings. Alternatively, one can disable the Overlay altogether, by unchecking "Enable the Steam overlay while in-game".