My Acer laptop monitor is having problems with the backlight, and I believe it is either the inverter or the actual backlight needs to be replaced.
I was changing settings in the display settings on my laptop, and without knowing what it was really for, checked off "Extend the desktop onto this monitor". I am not sure for which display I initially did it (laptop or external) but now when I go to use the external display to display what is on my laptop, all I get is the desktop of my laptop. I hope that was clear--if not, I can clarify if you want.
However, when I go to make it so that neither display has the "Extend the desktop onto this monitor" checked off, the other will be grayed out and I am unable to uncheck both. I am forced to have one or the other using just this window.
I have posted pictures. With the settings I have on these pictures, the monitor on the external display goes to sleep. If I have it so that the HP monitor is checked off and the other is grayed out, I just get a desktop of my laptop on the external display.