Paolo,
Fire up FS2004 (just on it's own, don't start the Flight Logger) and 'Create a Flight' at any field and using any aircraft (Cessna 182 is good for this).
When you get to the cockpit, ensure flaps are totally up, turn off all the lights and shut down the engines ('Ctrl+Shift+F1'), turn off the avionics, alternators and finally battery.
Save the flight exactly as you have it now (';'), and make this new flight the default. That's the preparation done.
Quit this flight and create a new one (a PP flight for instance, using the Flight Logger).
When you get to the cockpit for this new flight, your engines will already be off, as will all the lights, and you will have what is known in the trade as a "cold and dark" cockpit.
