I have bought an Intel NUC (NUC8i5BEH) along with 8 gigs of memory for my Wife.  My intent was to use an SSD out of an existing desktop that also had an HDD in it.  The problem is that on starting, the NUC reports no bootable device.  Looking in the NUC BIOS I see the SSD listed but cannot put it into the boot sequence.

On the (donor) desktop, the SSD (C) was bootable.  The HDD was H drive.  I used Partition Wizard to 'clone the OS' from C to H.  On restart I got into the BIOS and configured the disk unit that was H to the first bootable media.  The SSD was disabled.  PC Booted OK (HDD now C drive). Powered off the desktop.  Moved the SSD to the NUC and powered up for the first time and got the error as above.

The SSD seems to be working OK (otherwise the NUC BIOS would not see it) but the NUC BIOS thinks it is not a boot device.  My first thought is to create a bootable USB drive using the Windows 10 media creation tool, then try to find appropriate 'repair' options not dont involve re-installing windows.  The reason for avoiding a re-install is that my wife is an accountant and runs unsupported accounting software with no installer (ie xxx.exe) available.  She has spent the last 2 years getting around to moving to a cloud-based alternative but in the meantime....

I am aware of the driver issues associated with this approach but I have to give it a try.

Any suggestions that dont involve re-installing Windows welcomed.