Os not found and UEFI diagnostic tool

[Arunan1]

I wanted to enable secure boot .So I looked at the internet for instructions. It said that I had to turn it from Legacy to UEFI BIOS mode.But first I had to apply the mbr2gpt.exe. After applying, The PC shut downed and turning it on, hp PC diagnostic tool UEFI came. I exited and a message appeared saying,"OS not found". What should I do to solve this? 

[Paul_Tikkanen]

Hi:

Your notebook must have W10 installed in Legacy mode.

You would need to reinstall W10 in UEFI mode if you want to enable secure boot.

UEFI mode and secure boot require the hard drive be formatted with the GPT partition scheme.

Legacy mode uses the MBR partition scheme.

When you disabled Legacy mode, the PC wants to boot from a GPT-formatted drive and can't find such a drive to boot from.

Change the BIOS setting back to Legacy if you want to continue using the notebook without having to reinstall Windows in UEFI mode, or you want to copy your files off the drive before installing Windows in UEFI mode.

Installing W10 in UEFI mode would simply mean booting your W10 USB installation media from the UEFI USB boot source and not the Legacy USB boot source.

[Arunan1]

Can I go back to legacy mode in Uefi os not found?

[Arunan1]

I've chosen to go legacy. But how?

[Paul_Tikkanen]

The legacy mode setting would be in the F10 BIOS setup menu.

[Arunan1]

Which button should I press after f10? Will it bring me windows 10?

[Paul_Tikkanen]

After you are in the F10 setup option, there should be a legacy mode setting to enable and a secure boot setting to disable.

You need to enable legacy mode and disable secure boot.

Since I don't have your computer and there is no manual that shows the BIOS settings, you will have to figure it out on your own.

This is the closest document HP has for enabling legacy mode and disabling secure boot.

HP Notebook PCs - Cannot Start Notebook Computer From a Bootable CD or DVD | HP® Customer Support