I have an Inspiron 8200 which has suddenly decided not to display it's desktop full screen. On the Laptops own LCD screen, the desktop appears as a smaller square approximateley two thirds the size of the complete screen. Display resolution still reports that it is displaying at whatever resolution that it is set to, it's just not utilizing the whole screen to do so leaving a black border around the image.

Does anyone know the cause and solution to this problem please??