Windows Upgrade Help and more

Thanks! I checked and my drive is MBR. How do I change it to GPT without losing everything?

Has anyone else hit a wall trying to upgrade to Windows 11 because of Secure Boot? My PC meets all the other requirements, but the PC Health Check app says it's not enabled. I went into the BIOS (UEFI) and it *is* enabled, but I'm still getting the error. I’ve also seen a vague "This PC can't run ...