Wont boot with secure boot enabled

[BILBOHP]

When secure boot is enabled I cannot boot from the internal or any external drive, it tries and then displays boot device not found. If secure boot is disabled it boots okay but I need secure boot to be active.

I have tried replicating the setting of another laptop, same model which boots fine but no change.

I have updated to latest bios, reset bios, reset tpm, cleared and reset keys.

Is there anything else I can try?

[WAWood]

@BILBOHP 

Did you or anyone else reinstall Windows onto this laptop?

Asking because HP laptops that come with OEM Windows 10 preloaded come with Secure Boot enabled, and with UEFI boot as well.  So, if you then change to Legacy boot, the PC simply will no longer boot.

Since yours boots in Legacy mode, that means someone reinstalled Windows 10 onto it -- and used Legacy mode in the process.

[BILBOHP]

@WAWood

Thanks for your reply. Windows has been installed onto this machine a few times. This started occurring when hp replaced a fan, the hd was taken out and put back in as part of the process but I am taking the internal hd out of the equation as it is an external hard drive that I am trying to boot so I can re-install windows from that, and this same external hard drive boots fine when connected to another, same model laptop with the same secure boot settings, that is what has me stumped.

[BILBOHP · Accepted solution]

Further to my previous reply, I have established that it is the internal ssd preventing the system from booting even from a trusted external hd when it is installed. If I take the internal SSD out the external hd will boot in secure mode fine.

So how can I go about getting the laptop to trust the internal ssd again? Boot in legacy from external drive and run some diskpart commands etc?

Edit: Fixed - I used the bios hd utility to secure erase the interal ssd and I can now boot in secure mode from external drive and reload windows onto it. Phew.