If your computer is on and the display is black (not on), then you could have turned the display off by mistake. To turn the display back on hold the “Fn” key, and then press the “F5” key. Once you press both keys simultaneously, the display should turn back on.
If the process above does not fix the problem then the computer could be in “Projector Mode.” To convert it back to “Computer Only” mode, simply hold the “Fn” key then press the “F5” key. Then you will see the possible display modes, please select the “Computer Only” mode and your display should go back to normal.
Try checking out our [[Toshiba Satellite A665-S5170 Troubleshooting|troubleshooting guide]] for the Toshiba Satellite A665-S5170 if you have any more questions!