Shifting from BIOS to UEFI with the Windows 10 Creators Update MBR2GPT disk conversion tool

Bronze Contributor

Comprehensive yet quick video overview that explains how you can safely and non-destructively convert a Windows 10 machine from legacy BIOS to UEFI disk partitioning; and how you can automate the conversion as part of your in-place upgrade process from Windows 7 to Windows 10.

 

52 Replies

Tried a lot. 

I am getting an "unrecognized partition error".

Capture.PNGThis is my partition setup.

 

 

I have attached the log files below.

Somebody please help :(

There is a partition on the disk MBR2GPT doesn't like. Try running the following diskpart commands:

DISKPART> select disk 0

DISKPART> list partition

.

.

.

DISKPART> select partition 1

DISKPART> detail partition

.

.

.

(repeat for each partition)

 

You should be able to see which one is causing issues.

Mike, I hope you will spend a few minuttes looking over this, as I can't figure it out on my own.

Is the attached information sufficient?

 

Thanks in advance.

 

Diskpart overviewDiskpart overviewMBR2GPT validation and resultMBR2GPT validation and result

Error 0x0000057 means: The disk structure is corrupted and unreadable.

 

Try running chkdsk and see if it finds anything wrong with the disk.

No luck. ChkDsk reported no errors.
Still error 0x571

Btw. I never saw 0x57 - only 0x571

Sorry - typo on my part. 0x571 is what I meant to type. What make/model is the system and how was it built? If I had to guess, it is having an issue with the third partition. Type 39 is Bell Labs partition type.

I understand that the MBR2GRT.exe will support versions of Win 10 previous to 1703 and should work when booted from a Win PE 1703 disk.

 

So I downloaded & install Windows ADK 1703 & made a Win PE disk. I booted from that disk and ran MBR2GPT /validate and the result was "unable to validate disk." Any ideas? It's a 500gb disk with about 90gb free. Is free space the problem?

 

Larry Hess CAP | Albuquerque, NM | www.LarryHesscpa.com

Hi Mike,

 

It's a Dell Latitude E7450.
However, I think I've located the problem.

 

I created a new WinPE image, and now it works. The same system is converted, and BIOS settings changed, and now all is fine.

 

The new WinPE image is 10.0.15063 where the old one was 10.0.10240

Can you verify that mbr2gpt.exe will only run on WinPE images based on boot.wim from a 1703 media?

Yes - it requires WinPE from the ADK 1703 (there are other files that are necessary for it to run correctly). Plus, it is only supported to run on either WinPE 1703, Windows 10 1703 or later.

This makes sense as the conversion process will create one partition hence you at most can have three existing partitions. The documentation here:

https://docs.microsoft.com/en-us/windows/deployment/mbr-to-gpt

actually states:

There are at most 3 primary partitions in the MBR partition table

But, again a shoutout to Microsoft developers: The errors you (Developers) throw are not there for so only you can debug your code. They are first and foremost for the user to understand what has gone wrong. So the question remains: Why is there no error message on validation that states: There are too many partition on disk x, please reduce the number of partitions to at most 3 to be able to convert. --> This should not be that hard.

Hi,I can't convert it from MBR to GPT.

This is the error:

MBR2GPT: Attempting to validate disk 0
MBR2GPT: Retrieving layout of disk
MBR2GPT: Validating layout, disk sector size is: 512 bytes
Disk layout validation failed for disk 0

Thank you for your information. It's very helpfull.

MBR works with disks up to 2 TB in size, but it can’t handle disks with more than 2 TB of space. MBR also only supports up to four primary partitions — if you want more, you have to make one of your primary partitions an “extended partition” and create logical partitions inside it. This is a silly little hack and shouldn’t be necessary.
GPT stands for GUID Partition Table. It’s a new standard that’s gradually replacing MBR. It’s associated with UEFI — UEFI replaces the clunky old BIOS with something more modern, and GPT replaces the clunky old MBR partitioning system with something more modern. It’s called GUID Partition Table because every partition on your drive has a “globally unique identifier,” or GUID — a random string so long that every GPT partition on earth likely has its own unique identifier.

This system doesn’t have MBR’s limits. Drives can be much, much larger and size limits will depend on the operating system and its file systems. GPT allows for a nearly unlimited amount of partitions, and the limit here will be your operating system — Windows allows up to 128 partitions on a GPT drive, and you don’t have to create an extended partition.

On an MBR disk, the partitioning and boot data is stored in one place. If this data is overwritten or corrupted, you’re in trouble. In contrast, GPT stores multiple copies of this data across the disk, so it’s much more robust and can recover if the data is corrupted. GPT also stores cyclic redundancy check (CRC) values to check that its data is intact — if the data is corrupted, GPT can notice the problem and attempt to recover the damaged data from another location on the disk. MBR had no way of knowing if its data was corrupted — you’d only see there was a problem when the boot process failed or your drive’s partitions vanished.

For the people who are getting the following error when validating:

Cannot find OS partition(s) for disk X
First make sure you have the correct disk selected with the Windows installation.
 
If this is the case there is probably something wrong in your BCD configuration. If you have a simple single boot system, you can easily rebuild it from a elevated prompt with:
bcdboot.exe X:\Windows
After that it should validate just fine (it did in my case).
 
X is dependent on your system. In most cases 0 and C

Just done this on one of our work machines. If this works it'll save us bloody hours so cheers MS. One question though it seems to have gotten to "Fixing drive letter mapping" and stopped. Checking everything else it seems fine, disk converted , lovely... so is it safe to restart and change the BIOS/UEFI options or does this take a dam sight longer than the video hinted at?
Up to 40 minutes now.

I had some error..  I tried this mbr2gpt /validate /disk:1 /allowFullOS /logs:c:\temp\Errors 

  Error make sense, Msg="ValidateLayout: Too many MBR partitions found, no room to create EFI system partition." 

 

  4 primary and no extended is valid for MBR, but tool probably need space to create 1 new partition before conversion.

  other problem was not existence of Recovery partition - i just copied it from Windows 7 Efi instalation, is mostly just empty space - to backup image is few MB big.

This tool is very beta, poor coding, new error:

cannot rely on this space

 

<z:row Cls="D" Sev="50331648" Maj="Def" Min="Def" LN="4099" Fil="" Fun="pExecuteConversion" Uid="50331648" Msg="MBR2GPT: Partition final size is: 248640438272 (initial size was 248640438272), cannot rely on this space" PID="14424" TID="14612" Con="" Exe="C:\WINDOWS\system32\MBR2GPT.EXE" Mod="MBR2GPT.EXE" Err="0" MD="" DT="2018-04-10T20:48:51"/>

 

 Validation is succeffull.

I Just resolved the validation issue. 

basically you must not have more than three partitions and not any free space left on the hard drive.
if you check the list of partition on DISKPART you will see that even the free space is listed as a partition.
you can use tools like disk manager (built-in windows) or minitool to resize the current partitions to take up the left over free space then validate mbr2gpt again. 

hopefully it works for you too :) 

 

let me know

Here is what my HD looks like using DISKPART:

 

DISKPART> list volume

Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
Volume 0 E DVD-ROM 0 B No Media
Volume 1 C 790 SSD NTFS Partition 449 GB Healthy System
Volume 2 D Recovery NTFS Partition 15 GB Healthy
Volume 3 RAW Partition 856 MB Healthy Hidden
Volume 4 RAW Partition 455 MB Healthy Hidden

 

And the attached PDF shows what it looks like using the Disk Management extension of the Computer Management console.

 

How would you suggest dealing with these partitions in order to be able to sucessfully run MRS2GPT?

 

Here is what my HD looks like using DISKPART:

 

DISKPART> list volume

Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
Volume 0 E DVD-ROM 0 B No Media
Volume 1 C 790 SSD NTFS Partition 449 GB Healthy System
Volume 2 D Recovery NTFS Partition 15 GB Healthy
Volume 3 RAW Partition 856 MB Healthy Hidden
Volume 4 RAW Partition 455 MB Healthy Hidden

 

And the attached PDF shows what it looks like using the Disk Management extension of the Computer Management console.

 

How would you suggest dealing with these partitions in order to be able to sucessfully run MRS2GPT?