How to Restore Desktop to a Full Screen
If you are working on your computer and a graphical glitch occurs that forces the resolution of your desktop down to a smaller size than your screen, you may see a black box surrounding your Desktop image. You can get rid of this box and go back to a full screen on your desktop by manipulating the resolution settings on your computer.
Right click on an empty space on your Desktop.
Click "Properties" then click "Display."
Click "Adjust Resolution."
Click the "Resolution" dropdown and then change the resolution to the maximum setting.
Click "OK" to apply the settings change.