I would like to change my hard drive partition table from MBR to GPT,

(since MBR supports 4 primary partitions).

After some searching, I discovered C:\Windows\Panther\setupacl.log, and found a few interesting lines.

3 lines of interest:

1. Callback_BootEnvironmentDetect: Detected boot environment: BIOS

Meaning of BIOS / UEFI, I am using the old bios : BIOS

2. ConX::Compatibility::CSystemAbstraction::HostIsUEFIFirmware: Host is not UEFI.

Obviously I am not UEFI

And the particular line of interest

3. CHostIsUEFICompliantChecker: checked HostIsUEFICompliant, found NoIssue.

Since UEFI supports GPT and MBR, but does MBR support GPT?

I am curios to whether I am able to change to a GPT partition table with my current bios:BIOS and still be able to boot?


Obviously I am not UEFI

Not really. If your UEFI firmware has decided to boot the OS in BIOS-compatibility (CSM) mode, it'll also look like BIOS. It would be more reliable to look through the firmware's settings screen or documentation.

Also, when you try to boot from a CD or USB through the firmware's "boot menu", look carefully – often there will be two entries for booting a CD; one for UEFI mode and one for BIOS CSM mode.

(Also, if you're making a Windows installation USB yourself, be careful with unofficial tools. For example, Rufus will let you choose between making an UEFI-compatible and BIOS-only USB, while WinUSB doesn't support UEFI at all.)

but does MBR support GPT?

That question doesn't make sense.

I am curios to whether I am able to change to a GPT partition table with my current bios:BIOS and still be able to boot?

This is technically possible, assuming…

  1. …the BIOS supports it. Normally BIOS shouldn't care at all – it should just run the OS's bootcode from 0th sector and let that parse partitions on its own, whether they be in MBR or GPT.

    Unfortunately some BIOSes insist on having valid partitions in the MBR. And some will outright crash if they find a GPT. I guess you'll have to try and see.

  2. …the OS and its bootloader supports it. Linux can boot from such a combination just fine, but as far as I know, Windows cannot. (That is, Windows wants either UEFI+GPT or BIOS+MBR.)

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