THE VTR employs a Eurovox sound system familiar to purchasers of cars from a variety of European car-makers, including Citroen's sister car company, Peugeot. The six-speaker system includes an in-dash single-CD player, and AM/FM stereo. Of a cassette player there is no sign, the stereo offers 12 FM pre-sets, six AM pre-sets and all functions are operated by push-buttons. Annoyingly, the unit will not turn off when you shut down the engine and withdraw the ignition key. Why?