Invalid signature deteced. check secure boot policy in set up

[Rock75]

I forced turn off my desktop (HP Envy Desktop 750-624) because the screen was black. When I turned it on, it has a red message box that says: "Invalid signature detected. Check Secure Boot Policy in Set up". 

There is no other option but to click "OK"

Once I click "OK", it goes to a color blue box that says: "BOOT DEVICE NOT FOUND" "PLEASE INSTALL AN OPERATING SYSTEM ON YOUR HARD DISK", HARD DISK-(3FO), F2-SYSTEM DIAGNOSTICS.

I pressed F2, then it goes to HP PC HARDWARE DIAGNOSTICS UEFI and it has selections as follows:

-System Information

-System Tests

-Component Tests

-Firmware Management

-Test Logs

-Language

-Exit

From here it just kept repeating everything

[Bill_To]

Hi

That initially sounds like you have a Secure Boot issue but seeing a hard disk error suggests you have a corrupted boot disk (data) or a failing boot disk (hardware). Can you run diagnostics, system or component tests, or is the PC looping to the Secure Boot error again?

You could try disabling Secure Boot in the BIOS. Then check again. While there you should verify the disk is detected by the BIOS.

Or reset the BIOS to defaults. Then pull the CR2032 MB battery. Wait awhile. reinstall the battery. This will reset CMOS.

Or pull the disk. connect it to a different PC to see if you can mount this disk as a data drive. Copy needed data. Then reconnect to this PC.

See if you can reinstall Windows. Or try a different drive when reinstalling Windows.