To switch back to 2D while playing the game in 3D you can use the "3D On/Off" hotkey. By default this is mapped to "Alt+Shift+-". Alternatively, you can open the TriDef 3D Ignition OSD, navigate to the "3D" menu and turn 3D off.
The TriDef 3D Ignition game driver is only loaded when the game is launched from an icon in the TriDef 3D Ignition application interface. To launch the game in 2D without using the TriDef 3D Ignition game driver, simply run the game from its original shortcut in the Start Menu or Desktop.