How to convert MBR to GPT and change from BIOS/legacy boot to UEFI

Solution 1:

This is resolved now. I could not get mbr2gpt.exe to work BUT I was able to get GDisk to work (online documentation is bad, overly verbose and long winded, but just boot to WinPE and run the GDisk64.exe for command discovery): http://www.rodsbooks.com/gdisk/mbr2gpt.html

• Download GDisk, copy gdisk-windows-1.x.zip to USB that has Win10 ISO on it, then extract the .zip to a folder
• UEFI boot to Win10 ISO > CMD prompt. Use DISKPART to check OS disk number (it's typically 0), list volume (to find USB drive)
• Open CMD and cd to the GDisk directory you made on the USB drive
• Run GDisk against disk 0 like so: gdisk64.exe 0:
• Type "Y" to start GDisk, then "?" to display commands
• w = write table to disk and exit

Once this is done your partitions have been converted from MBR to GPT, but your system partition (boot loader) is now broken. Follow the steps here to recreate it: https://social.technet.microsoft.com/wiki/contents/articles/14286.converting-windows-bios-installation-to-uefi.aspx

Finally, change your BIOS boot mode to UEFI and you're done!