Hi. I assume that you are pressing the key sequence to switch to external monitor (usually ctrl+ "key with pic of monitor")
If you can see that everything else works and that there is the usual disk activity at boot up and you cant get an external monitor to work on it. then you need to take it to a specialist for diagnosis or return it to the shop or manufacturer if it is still under warranty.
seems like your graphics adapter has failed and as it is part of the laptops mainboard means you cant just remove it and test it, so you should have specialist diagnose it for you>