I recently picked up a 1TB NVMe drive that I wanted to use as my windows drive. So I tried a couple different cloning programs untill I got one that worked. After the clone was complete I unplugged the old SATA drive (as suggested somewhere) and booted into Windows succesfully with the new NVMe drive. Happy with the results I turned the computer off and plugged in my old SATA drive. I ensured that the boot settings in bios were to boot from the NVMe drive. It would not boot into windows. I forget the error it gave me (I'm sorry). I went back into bios to check things again to ensure that it wasn't trying to boot from the SATA drive. It was not. I tried to boot again and it would not boot into windows. I again turned off the computer and disconnected the SATA drives to see if it would boot from the NVMe drive like it did previously. Now it would not boot from the NVMe drive either! Out of frustration, I just removed the new NVMe drive and my computer has booted and is running off the original SATA HD. Any ideas as to what could be happening? It's strange it would boot from the NVMe drive once, but not again and also not boot from the original SATA HD with the correct boot sequence selected.