I have a HP Pro 3330 MT PC with Windows 10 64-bit, 8GB of RAM and a SSD. I tried to boot into the BIOS to switch to UEFI. I accessed the Boot Order and saw two sections: "UEFI Boot Sources" and "Legacy Boot Sources" but I can't move my disk with Windows 10 installed to the "UEFI Boot Sources" section and I can only move its order in the "Legacy Boot Sources" section. Can anyone explain?
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1 Answer
Your existing Windows 10 installation was installed in legacy BIOS mode, which means the partition structure on the SSD is MBR rather than GPT. You can only boot Windows 10 in UEFI mode if the structure is set to GPT.
Microsoft created a tool (MBR2GPT.exe) which can help you convert your existing MBR installation to GPT. After the conversion, it will only boot in UEFI mode, and no longer boot in legacy BIOS mode.
It would be a good idea to have a full system-image backup before making this change (e.g. CloneZilla, MacriumReflect).
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So if I convert my disk to GPT then the disk will appear in the "UEFI Boot Sources" section? I'm a bit afraid that BIOS will still list the disk in the "Legacy Boot Sources" section Commented Oct 10, 2020 at 5:52
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Yes, it should show up in the "UEFI Boot Sources" section after converting it to GPT. Please make a backup first. If you do a search on SuperUser for mbr2gpt, you'll see that some people are left with a bricked system. If you have a system-image backup, it is easy to revert back.– James TCommented Oct 10, 2020 at 6:00