Since Windows 10 (1703 build 15063 – Creator’s Update) Microsoft natively supports conversion from MBR to GPT via MBR2GPT.exe tool. If you want to proceed with conversion of OS disk and switch Bootable mode from BIOS to UEFI then follow these steps:
Convert Windows OS Drive from MBR to GPT because of switch from BIOS to UEFI
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Tutorial how to convert Windows System disk from MBR partitioning scheme to GPT (GUID Partition Table) without data loss in Windows Server 2012 R2.