I have a Dell Inspiron 7559. The display is appearing on an external monitor. But I get no display at all when I disconnect the external monitor. And when I try to switch to the main display or duplicating the display with the external monitor connected, it gives an error telling me that the display settings could not be saved. The monitor does not seem to have any issues as the bios logo is displayed properly when I boot it up.
If it shows bios but not Windows, then it is possible that is the GPU that the attached display is using, and the external is using different graphics.
A way to test this would be to try and start the laptop in "Safe Mode". If it loads fine and shows on the laptop display fine, then you likely need to have your GPU replaced.
If the laptop is under warranty still, then contact the manufacturer. If it isn't, then try a local tech for the work.
How to enter "Safe Mode" when booting the computer.
In Windows 8 and 10...
As your computer restarts, press F8 (possibly a few times) to enter "Safe Mode"
a. Press the "F4" key to Enable "Safe Mode".
(The computer will then start in "Safe Mode" with a minimal set of drivers and services.)
b. Press the "F5" key to Enable "Safe Mode" with Networking.
( Once "Safe Mode" with Networking starts, Windows is in Safe Mode, with additional network and services for accessing the Internet and other computers on your network.)
c. Press the "F6" key to Enable "Safe Mode" with Command Prompt.
(In "Safe Mode" with "Command Prompt" starts Windows in Safe Mode, with a Command Prompt window instead of the Windows interface. This option is mostly only used by IT professionals.)
Now sign in to the computer with your account name and password. (If you have one set.) When you are finished troubleshooting, you can exit "Safe Mode" restarting your computer.
In Windows 7/Vista/XP...
1. Immediately after turning on the computer, or restarting it (usually after you hear your computer beep), tap the F8 key, repeatedly, in 1 second intervals.
2. The computer will then display hardware information and run a memory test.
3. Next the "Advanced Boot Options" menu will appear.
4. In the "Advanced Boot Options" menu use the arrow keys to select "Safe Mode" or "Safe Mode with Networking" and press ENTER.