Convert MBR to GPT - MBR2GPT fails with error 0x00000000

I've been trying to convert my OS drive from MBR to GPT for 3 days so I can enable secure boot. OS is windows 10 Pro, 21H2. Laptop is a Samsung NP930X5J. Original SSD was 256 GB; I imaged it to a 1TB SSD many years ago using Acronis, replicating the whole disk (4 partitions), expanding the main partition to fill the larger SSD. System has been working trouble-free for ~8 years. Original system was Windows 8.1 pro, upgraded to Windows 10 pro a long time ago. No dual-boot, nothing fancy at all.

When I first ran the following command: mbr2gpt /validate /allowOSfull I got "Disk layout validation failed for disk 0". After days of experimenting, I eliminated one of the 4 partitions (a 100MB partition that had virtually nothing in it) and after that, I was able to get a 'validation completed successfully'.

So then I tried mbr2gpt /convert /allowfullOS. The command failed with this error:

Code:

C:\WINDOWS\system32>mbr2gpt /convert /allowfullOS

MBR2GPT will now attempt to convert the default book disk.
If conversion is successful the disk can only be booted in GPT mode.
These changes cannot be undone!

MBR2GPT: Attempting to convert disk 0
MBR2GPT: Retrieving layout of disk
MBR2GPT: Validating layout, disk sector size is: 512 bytes
MBR2GPT: Trying to shrink the OS partition
MBR2GPT: Creating the EFI system partition
MBR2GPT: Installing the new boot files
MBR2GPT: Performing the layout conversion
Cannot perform layout conversion. Error: 0x00000000
MBR2GPT-undo: Removing the EFI system partition
MBR2GPT-undo: Extending back the OS partition
MBR2GPT: Conversion failed

System boots fine into Windows 10 in this configuration; I just can't convert to GPT.

I'm now heading down the rabbit-hole of pursuing the 0x00000000 error, but would appreciate any insight from anyone out there! Thanks.

Ghot said:

Hello @Steerpike58, welcome to TenForums.

Please post a screenshot of Disk Management, as shown below...

Thanks for following up! Here is a screenshot from Disk management:



The 16 GB OEM Partition was originally labeled 'SAMSUNG_REC' and contained a bunch of Samsung stuff. The 525 MB 'Recovery Partition' contained only 'recovery' folder. I'm willing to lose those partitions, though I'd like to still have the ability to go to Settings / update and security / recovery / advanced startup, and have troubleshoot / Advanced options / Command prompt available, if possible (they ARE available now). I believe they rely on some of those partitions being available. I can no longer use F4 on boot to directly enter the recovery console.

Edit To Add: found this post that provides a very detailed solution, though it seems specific to Dell. I get the sense my issues are relating to the Samsung recovery stuff that was there from the beginning. Is it possible to recreate a 'recovery' partition 'after the fact'? MBR2GPT conversion 0x00000000 Error - General Hardware Forum.

Ghot said:

It may be the OEM partition.

Have you tried to do the conversion with Minitool Partition Wizard (free)?

Best Free Partition Manager for Windows | MiniTool Partition Wizard Free

How to...
How to Convert MBR to GPT without Data Loss in Windows 7/8/10

...

I have been trying with MiniTool Partition Wizard (Free) but - as soon as I select the mbr2GPT option, up pops the screen to get me to license the 'professional' version. Tried several times. So the fact that their guide says you can do this with 'free' version seems to be incorrect, unless I'm missing something! I believe I tried AOMEI's free version also; same issue.

EDIT TO ADD: I don't mind paying $59 for the tool but it says the license is for '1 PC'. I have two identical PCs, and all I want to do it convert them to GPT so I'd prefer not to pay $59 twice, just for this feature. If by '1 PC' they mean, concurrently, then I can do one then the other but if they are super strict about it, could be a pain.

My actual goal here is to take one of my old Samsung NP930X5J's (which have been rock-solid) and use it as a test bed for upgrading to, and then playing with, W-11. I already have 2 new W-11 laptops but I want a third to really 'experiment' destructively on!

- - - Updated - - -

SIW2 said:

is the full model number of your laptop Samsung NP930X5J ?

I think there was a program for doing that , but iirc there were several versions of samsung recovery solutions.

it is called admin tools for samsung recovery.

The full, full model number is NP930X5J-S01US, but the last bits denote things like SSD size, ram size, etc. There were two main models in the family - NP930 and NP940. The 940's had touchscreens, the 930's did not. X5J's were 15.6" screens.

For a time, Samsung had a really good 'download' site for this model but now it's long gone.

It can be done with diskgenius free versiosn.

It is not automated. You need to run it from another os ( or winpe) point it at the disk and convert to gpt.

Then use it create an esp partition in unallocated space. Then run bcdboot command to populate the esp partition with the boot files.

I have done it several times only takes a couple of minutes.

I have never tried it on something with a weird partition id like yours seems to have.

there is probably a giveaway of one year license for aomei partition assistant pro if you look around. I have used that a couple of times without any problem.

here:
AOMEI Partition Assistant Pro ? ?????????? ????????

if you already have version 9.15.0 installed, just enter the key provided at that page.
apparently it lasts forever, but only gets upgrades till the end of the year.

looks like the registration period has expired.