UEFI boot is disabled, disabling Legacy boot does not work

Question

On my computer, I enabled Legacy boot to use older operating systems (even though I did not install any). A few weeks later, I could not find UEFI boot on my hard drive. I get "Notebook Hard Drive" is my boot menu, but do not get "OS Boot Manager". Disabling legacy boot does not help. When I do, I get:

Boot Device Not Found

Please install an operating system on your hard disk.
Hard Disk (3F0)
F2   System Diagnostics

For more information, please visit: www.hp.com/go/techcenter/startup

When I look at the Boot Option Menu (accessible by pressing F9), it is blank. It reads:

-------------------------------------------------------------------------------------------
                                      Boot Manager
-------------------------------------------------------------------------------------------

Boot Option Menu


UP and Down to change option, Enter to select an option.
Press F10 for BIOS Setup Options, ESC to exit.

Not even the ability to select EFI file.

I have tried resetting BIOS settings, but it did not fix the issue.

I have Linux Mint 18.3 (Cinnamon 64-bit) installed. It came with Windows 8.1 from the factory. It can still boot Linux with Legacy boot enabled, even though it used to work on normal boot.

My computer is an HP 10 TS notebook computer, (model e010nr I think), with InsydeH2O BIOS version F.0A (16.010?) revision 3.7. System Board ID 21A9.

Answer 1

There are BIOS level UEFI entries that need to exist for the boot process to know where your Windows Boot Manager lives.

With the board in UEFI only mode, look at your boot options. There should be an option to "Add new boot option". This allows you to edit the UEFI menu on your motherboard.

Without knowing the brand of your firmware I cannot provide better instructions. Please read the manual for your motherboard.

EXAMPLE: https://www.thomas-krenn.com/en/wiki/Restoring_UEFI_boot_entry_via_motherboard_replacement_or_BIOS_update