For future reference,

I carried out those commands, but from inside Windows. I then restarted the PC, and booted from the Windows USB installer, and pressed Shift+F10 to bring up a CMD when the...

Thanks for your help! So after doing this, can I now delete the EFI partition from the other HDD? Is there a concern to worry about setting the SSD partition as active?

I recently upgraded my laptop with an SSD, moving my older HDD into the optical drive bay. I then installed Windows 10 from a UEFI USB (using the Windows 10 media creation tool), on my SSD (with the...