HP won't turn on

[Erika5]

Laptop wont boot up after failed factory rest. Reser got to between 34% and 54% and failed. Now laptop wont boot up pops up with the HP screen then goes back and forth with black screen (in between the hp and black screen a grey screen pops up with a white underscore in the top left hand corner and no words or letter pop up goes straight to the hp screen and does the cycle all over again). 

[Lil_Boy_Blue]

Hi
First:- Turn off the computer, press and hold the PWR button for 4 seconds.

Then - Leave only keyboard and mouse connected, disconnect all externally connected
devices such as Docking Station, USB storage devices, displays, and printers.
Unplug the AC adapter from the computer.

Next - Press and Hold the Power button for 15 seconds to Hard Reset.
Rinse and Repeat

NOW begin checking/testing/proving the Hardware is fit for purpose.

Power on your PC, press ESC (repeatedly), then F2 at the prompt.
Choose System Tests (Fast Test does a 4 minute hardware check).
AND/OR
HOW DO I USE DIAGNOSTICS?

HP PC Hardware Diagnostics Windows is a Windows-based utility that allows you to run diagnostic tests to determine if the computer hardware is functioning properly. The tool runs within the Windows operating system in order to diagnose hardware failures. HP PC Hardware Diagnostics Windows comes pre-installed on new HP computers, but if not on yours, download here:- http://ftp.hp.com/pub/softpaq/sp93001-93500/sp93457.exe