Just a quick note for the internet at large: to remap the zoom, favorites, shortcut buttons, etc. on a Microsoft Natural Ergonomic Keyboard 4000, when using Apple OSX, you need to use USB Overdrive.

Just open the preferences pane, and hit the special key you want to modify. It appears in the list, and you can remap it to anything. Extremely useful.

EDIT: For a more complex solution, which is powerful but harder to learn, try ControllerMate.