Some time when we convert windows from Physical to Virtual we lost the information about the boot loader system not knowing if to create EFI or MBR Virtual Machine, with hyper-v It is the different between generation 1 and Generation 2 type of machines, there is few ways to tell, the first one is to go to the system logs :
start the VM with installation disk or any other disk allowing you to access c:\windows :
cd C:\Windows\panther
notepad setupact.log
look for Callback_BootEnvironmentDetect
FirmwareType 1 = MBR
FirmwareType 2 = EFI
you can also run bootedit /enum as administartor and find under “Windows Boot Loader” the value “path” should have winload.exe for MBR or winload.efi for EFI
You can also try mount the disk on host system and check in the disk manager the version :
OR
Thanks for the post, very useful.
Just add, with Windows 10, it is possible to convert from MBR to GPT without formatting:
http://www.sysadmit.com/2017/12/windows-convertir-mbr-bios-gpt-uefi-sin-perder-datos.html
With EaseUS it is possiable
https://www.easeus.com/partition-manager-software/convert-mbr-to-gpt-gpt-to-mbr-using-cmd-without-losing-data.html
This services is Good