Ah well Windows 10 won't boot off the old drive in the new motherboard. Seems it may be to do with the partition type MBR on the disk but GPT may be required now. It should be possible to set to legacy in the BIOS but it doesn't seem to be there. Looks like it will be necesssary to do something like this ...
https://learn.microsoft.com/en-us/wi...nto-a-gpt-disk