PC locked on HP PC Hardware Diagnostics UEFI screen

[Bludgeon]

I hadn't turned my laptop on for 2 days. When I did, it had lots of work to do. Then it wouldn't shut itself off. I turned it off improperly I suppose. Then I couldn't get past the Welcome screen. So, I tried some hp instructions like pressing the esc key then F2. Got it to respond. Got to the HP PC Hardware Diagnostics UEFI page to select English and now the screen is locked.

[CF4]

Please 1st try a Hard Reset

Press and Hold the PWR off button for 4 seconds to force a PWR off.

Unplug from the wall.

If you see a battery compartment door, your computer has a removable battery.

Remove any removable battery.

This is valid for most notebooks;

Press and hold the power button for 15 seconds to complete the reset.

Re-insert any battery you removed.

[Bludgeon]

My computer does not have a removable battery. But I held the power button down and it appears to be rebooting.  It got to the Welcome Screen. Now it is all black. I had an issue before. We'll see what happpens.

But, thank you so much for your instructions. Do you know what I should do if the screen stays black?

OMG! I got my desktop screen back! I'd been unable to get that all night last night! I'd turned the thing off erroneously.  My HP quesion mark icon has and exclamation mark. I'm going to click on it.

Muchas Gracias, Distinguished Professor!

[CF4]

Prego.

MAKE BACKUPS.

MAKE RECOVERY MEDIA.

ELSE make your own from MS

ISO images of various Microsoft OS's are available.

They can be be downloaded (sometimes you need a licence key other than the HP OEM key)
and 'burnt'/expanded to a DVD/USB. They WONT contain appropriate HP software, like drivers etc.
But may enable a repair to be started.
https://www.microsoft.com/en-us/software-download/windows7
https://www.microsoft.com/en-us/software-download/windows8
https://www.microsoft.com/en-us/software-download/windows10

For when it’s a NON MS OS (iOS/Linux/Android) to create install media.
www.microsoft.com/en-us/software-download/windows10ISO
and a HOW2 is here...
http://www.thewindowsclub.com/install-windows-10-from-usb

Just in case there is a next time.

[ericjem]

The response has been so helpful to me. 

It instantly worked. 

The trick is that after replacing the battery and it brings back that black screen, you select exit and confirm. 

It works.