Quite suddenly, for some unknown reason, my Inspiron 8100 laptop screen has begun toe display only a half-sized window (measured diagonally) in the center of the screen. I have tried to change screen resolution, reboot in Safe Mode, and reboot in VGA screen. In Safe Mode, the window displays in full screen, so it doesn't seem like a hardware problem. But as soon as I reboot in regular mode, the window display reverts to a squeezed size. Can anyone suggest a setting or procedure that I might try to get the window to occupy the entire screen?

Thanks for your help.