Just seen your video,
You tried to run Dell Offline Diagnostic to check Hard drive and other Hardware within the computer? If no, then please follow steps below:
1. Power off computer. Remove all peripherals such as Flash drive, external driver or spealers.
2. Power on computer, quickly start tapping F12 continuously until you see Preparing One Time Boot Menu in top right corner of screen. In Dell Preboot menu, select Diagnostic. Report back any error code.
Note: Please don't wait until the Dell logo to appears to start tapping F12 key, soon as you power on computer, quickly start tapping F12 key. Got to be quick with the fingers for this step to work.