Solved MBR to GPT

zbook · Nov 3, 2024

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cereberus · Nov 4, 2024

bobkn said:
Dumb, no.

Conversant? Maybe.

I guess I've never installed Win 10 or 11 on an MBR disk. AN MBR disk lacks the 100GB EFI Boot partition? That would make the conversion a bit more awkward.

mbr2gpt sorts this out.

gaffar · Nov 4, 2024

If someone has legacy BIOS that does not support GPT, should they convert to GPT?

cereberus · Nov 4, 2024

gaffar said:
If someone has legacy BIOS that does not support GPT, should they convert to GPT?

This is like asking:

My car uses diesel. Should I put petrol in it?

What do you think the answer is?

jaylob4 · Nov 4, 2024

gaffar said:
If someone has legacy BIOS that does not support GPT, should they convert to GPT?

I'm not an expert not even that much PC savvy, but from what I have read recently, it's doable but not recommended.

If your PC is aged or supports legacy BIOS only and your OS is stable, don't bother converting.

Convert if you intend to upgrade to Win 11 and can bypass Microsoft's system requirements for OS upgrade.

But please read my opening sentence again.

jaylob4 · Nov 4, 2024

OK, a lot for me to digest in recent replies.

Disc 0 is my OS, disc1 is a clone of disc 0 made recently before replacing my PC hardware.

Before I do anything--anything, I am going to create a system image, not a clone.

Should I convert disc 1 to GPT before creating a new system image, taking into account disk 0 will, for a little while longer remain MBR?

Converting disc 1 to GPT will wipe everything on it after which it will only ever be used to store system images, nothing else.

After conversion do I need to create a new partition/s, do I need to create a space for ESP?

Disc 1 is an external SSD, does this matter for converting, making system images or deleting/creating partitions?

See image below as things stand.

Bree · Nov 4, 2024

gaffar said:
If someone has legacy BIOS that does not support GPT, should they convert to GPT?

Legacy BIOS requires that the boot drive is MBR, it cannot boot from a GPT drive. Windows itself supports GPT for any other non-boot drive though.

Legacy MBR boot isn't able to recognize GUID Partition Table (GPT) disks. It requires an active partition and supporting BIOS to facilitate access to disk.

Switch from legacy MBR disk to GPT disk with Windows 10 - Windows drivers

Provides guidance to enable a seamless upgrade and enable the user to apply new and improved security features of Windows 10.

learn.microsoft.com

jaylob4 said:
If your PC is aged or supports legacy BIOS only and your OS is stable, don't bother converting.
Convert if you intend to upgrade to Win 11 and can bypass Microsoft's system requirements for OS upgrade.

If your PC is legacy BIOS only and you'd have to use workarounds to clean install or upgrade, then don't convert. You need MBR to be able to boot, Windows 11 can run from an MBR drive.

SIW2 · Nov 4, 2024

jaylob4 said:
OK, a lot for me to digest in recent replies.

Disc 0 is my OS, disc1 is a clone of disc 0 made recently before replacing my PC hardware.

Before I do anything--anything, I am going to create a system image, not a clone.

Should I convert disc 1 to GPT before creating a new system image, taking into account disk 0 will, for a little while longer remain MBR?

Converting disc 1 to GPT will wipe everything on it after which it will only ever be used to store system images, nothing else.

After conversion do I need to create a new partition/s, do I need to create a space for ESP?

Disc 1 is an external SSD, does this matter for converting, making system images or deleting/creating partitions?

See image below as things stand.

If you want to make an image of your current system, you could store the image file on G . There is space. That way you have both the clone and the image.

Then you could give mbr2gpt a go at converting disk 0 to gpt. It looks straightforward from your diskmgmt screenshot. If mbr2gpt is a bit petulant, the manual method is the way to go. Should be easy enough as you have the 100mb system partition.

cereberus · Nov 4, 2024

SIW2 said:
If you want to make an image of your current system, you could store the image file on G . There is space. That way you have both the clone and the image.

Then you could give mbr2gpt a go at converting disk 0 to gpt. It looks straightforward form your diskmgmt screenshot. If mbr2gpt is a bit petulant, the manual method is the way to go. Should be easy enough as you have the 100mb system partition.

There is a slight snag with the layout as it is using four primary partitions.

You can only convert using mbr2gpt if there are three primary partitions as it has to create a fourth one (the EFI).

If you have 4 primary partitions, it cannot create a 5th one (EFI) as you can only have 4 mbr primary partitions.

(I do not know why it creates the EFI first before deleting the system partition - I guess it is so it can revert to mbr if the conversion fails).

However, this is not a big deal as you have the NTFS Recovery Partition which is not that important.

Use admin command "reagentc /disable" to move winre.wim to the C drive, and then delete the recovery partition.

You will now only have only 3 primary partitions and mbr2gpt should work fine.

After that, you can recreate the recovery partition if you wish but not that important as winre.wim is on C drive.
Alternatively, you can just run "reagentc /enable" and winre.wim gets moved to C:\recovery folder instead of a separate partition. It works just the same.

I have used mbr2gpt many times - providing you only have 3 primary partitions and no logical partitions (which you haven't) it should work fine and is also very quick as it is not moving bulk data around.

I would definitely try this first (making an image backup of whole drive).

An alternative strategy would be to backup D drive and delete that partition rather than the recovery partition (you would not need to run the reagentc commands).

jaylob4 · Nov 4, 2024

cereberus said:
There is a slight snag with the layout as it is using four primary partitions.

You can only convert using mbr2gpt if there are three primary partitions as it has to create a fourth one (the EFI).

If you have 4 primary partitions, it cannot create a 5th one (EFI) as you can only have 4 mbr primary partitions.

(I do not know why it creates the EFI first before deleting the system partition - I guess it is so it can revert to mbr if the conversion fails).

However, this is not a big deal as you have the NTFS Recovery Partition which is not that important.

Use admin command "reagentc /disable" to move winre.wim to the C drive, and then delete the recovery partition.

You will now only have only 3 primary partitions and mbr2gpt should work fine.

After that, you can recreate the recovery partition if you wish but not that important as winre.wim is on C drive.
Alternatively, you can just run "reagentc /enable" and winre.wim gets moved to C:\recovery folder instead of a separate partition. It works just the same.

I have used mbr2gpt many times - providing you only have 3 primary partitions and no logical partitions (which you haven't) it should work fine and is also very quick as it is not moving bulk data around.

I would definitely try this first (making an image backup of whole drive).

An alternative strategy would be to backup D drive and delete that partition rather than the recovery partition (you would not need to run the reagentc commands).

Thank you.

I read your replies but they are over my head, it's not you it's my lack of knowledge, others will know what you mean, I don't.

cereberus · Nov 4, 2024

jaylob4 said:
Thank you.

I read your replies but they are over my head, it's not you it's my lack of knowledge, others will know what you mean, I don't.

Just use alternative strategy - backup D drive partition it, delete it, use mbr2gpt, restore d drive backup.

It is that easy.

SIW2 · Nov 4, 2024

OP diskmgmt screenshot

jaylob4 · Nov 4, 2024

SIW2 said:
If you want to make an image of your current system, you could store the image file on G . There is space. That way you have both the clone and the image.

Then you could give mbr2gpt a go at converting disk 0 to gpt. It looks straightforward from your diskmgmt screenshot. If mbr2gpt is a bit petulant, the manual method is the way to go. Should be easy enough as you have the 100mb system partition.

Thank you, taking into account what @cereberus wrote above and I more or less understanding what you write and how, makes me think I can do that.

To achieve what I want in my post above, what is my best option/s.

Megahertz · Nov 4, 2024

gaffar said:
If someone has legacy BIOS that does not support GPT, should they convert to GPT?

If you use it as data only (not boot able) yes you can but not necessary should.
If boot able you must install the boot manage on another MBR drive and point the OS on the GPT drive. In this case it can be done but no, you shouldn't.

Megahertz · Nov 4, 2024

The easiest way is to convert using mbr2gpt. It will convert the drive to GPT, will shrink C: in 100M and create a EFI Fat32 partition and install the boot manager on it. It wont create the MSR (16M) that Microsoft says it's necessary and most of us don't.
To work, mbr2gpt requires that all system partitions (System, C: and recovery) are on the same drive.
The down side is that the partitions won't be on the current correct order and there will be a useless System partition.

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The method that Bree suggested will create all partition on the correct order

SIW2 · Nov 4, 2024

jaylob4 said:
Thank you, taking into account what @cereberus wrote above and I more or less understanding what you write and how, makes me think I can do that.

To achieve what I want in my post above, what is my best option/s.

If you are a scaredy cat I would suggest a third party program to create an image of your current system and store it on G. Then you still have the clone you already made and the image file sitting on G as well.

You can choose to use mbr2gpt to convert disk 0. If it works, it will shrink C and create a little esp at the end of C. Iirc the original 100mb stays where it is.

Or if you would rather have the esp at the start of the disk use the manual method.

Or another possibilty is use mbr2gpt and at a later date change the original 100mb to esp and get rid of the one mbr2gpt created.

jaylob4 · Nov 4, 2024

SIW2 said:
If you are a scaredy cat I would suggest a third party program to create an image of your current system and store it on G. Then you still have the clone you already made and the image file sitting on G as well.

You can choose to use mbr2gpt to convert disk 0. If it works, it will shrink C and create a little esp at the end of C. Iirc the original 100mb stays where it is and does nothing.

Or if you would rather have the esp at the start of the disk use the manual method.

Or another possibilty is use use mbr2gpt and at a later date change the original 100mb to esp and get rid of the one mbr2gpt created.

, made me smile, well, curiosity killed the Cat and while remaining curious of many things, age has taught me to keep my curiosity in check, nowadays I'd rather not be a dead Cat or in other words have a dead OS or worse no OS cos' I gone done something stupid, better to ask questions first.

I would like to give conversion a go manually following your previous posts which I more or less understood but may end up using the mbr2gp method.

Which is better, to have the ESP at the beginning or end or makes no difference?

Megahertz · Nov 4, 2024

jaylob4 said:
Which is better, to have the ESP at the beginning or end or makes no difference?

Makes no difference, but it is better to have C: next to the Recovery partition,

cereberus · Nov 4, 2024

SIW2 said:
If you are a scaredy cat I would suggest a third party program to create an image of your current system and store it on G. Then you still have the clone you already made and the image file sitting on G as well.

You can choose to use mbr2gpt to convert disk 0. If it works, it will shrink C and create a little esp at the end of C. Iirc the original 100mb stays where it is.

Or if you would rather have the esp at the start of the disk use the manual method.

Or another possibilty is use mbr2gpt and at a later date change the original 100mb to esp and get rid of the one mbr2gpt created.

Oops misread OP layout.
Should have gone to specsavers LOL.

As OP only has 3 primary partitions, mbr2gpt should work fine

Megahertz · Nov 5, 2024

Before you do the conversion to GPT I strongly recommend that you make the Recovery partition at least with 1G or you will have future problems

Open a CMD window as administrator and type:
(you can copy and paste each command to the CMD window)
Reagentc /disable (very important. Don't miss this cmd)
diskpart
sel disk 0
list part (identify the Recovery partition number n3 and windows partition number n2)
sel part n3 (replace n3 with the Recovery partition number found above)
del part override
sel part n2 (replace n2 with the Windows partition number found above)
shrink desired=484 (will result a 1020M unallocated space)
create par prim (will create a 1020M partition)
format quick FS=NTFS label=Recovery
set id=de94bba4-06d1-4d40-a16a-bfd50179d6ac
gpt attributes=0x8000000000000001
assign letter=R
exit
R:
MD R:\Recovery\WindowsRE
Reagentc /setreimage /path R:\Recovery\WindowsRE
reagentc /enable
reagentc /info

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