keithjr said: View Post
At the moment, I have restored the original MBR setup, so I am back where I started. So I have to decide on best way to try again. Either Partition Wizard Pro, or the mbr2gpt routine described earlier. Still have some unanswered questions on that one. See posts 5 & 6.
Just make the conversion with mbr2gpt and reboot.

The system may just boot, without doing any change in the firmware configuration.

If the system does not boot, reboot to the firmware setup and disable the CSM module or legacy mode. The UEFI or "UEFI only" boot mode should become enabled. It does not matter if Secure Boot is enabled or disabled. Save the configuration and reboot.