I am hoping a Windows boot expert can help me here as I am close to tearing my hair out 
I am running a fairly old Q77 motherboard with limited UEFI support. I have a SATA SSD (Samsung 850) and a PCI-E SSD (Samsung XP941 on PCI-E adapter card).
Windows refused to install onto the XP941, claiming it was not bootable. It did not show up in the BIOS boot devices, so I hacked the BIOS to add in the drivers/modules and now the XP941 shows up in the boot device list.
Windows still refused to install with the same error.
Installed Windows 10 onto the 850 and then cloned both partition over to the XP941.
Used EasyBCD 2.4 to add in an option to boot from the XP941.
Doesn't work: selecting the XP941 boot from the Win10 boot loader results, after a timeout, with a generic 'please insert valid boot disk' type message.
So the question I have for the experts:
I am not sure what I need to do to check if the XP941 has all that is necessary to boot. Can anyone help with this?
I am working on the assumption/hope, that if this issue is fixed, then it may be possible to boot directly to the XP941 and remove the 850 dependency.
Thanks for your help
I am running a fairly old Q77 motherboard with limited UEFI support. I have a SATA SSD (Samsung 850) and a PCI-E SSD (Samsung XP941 on PCI-E adapter card).
Windows refused to install onto the XP941, claiming it was not bootable. It did not show up in the BIOS boot devices, so I hacked the BIOS to add in the drivers/modules and now the XP941 shows up in the boot device list.
Windows still refused to install with the same error.
Installed Windows 10 onto the 850 and then cloned both partition over to the XP941.
Used EasyBCD 2.4 to add in an option to boot from the XP941.
Doesn't work: selecting the XP941 boot from the Win10 boot loader results, after a timeout, with a generic 'please insert valid boot disk' type message.
So the question I have for the experts:
I am not sure what I need to do to check if the XP941 has all that is necessary to boot. Can anyone help with this?
I am working on the assumption/hope, that if this issue is fixed, then it may be possible to boot directly to the XP941 and remove the 850 dependency.
Thanks for your help