Forum Discussion
Shifting from BIOS to UEFI with the Windows 10 Creators Update MBR2GPT disk conversion tool
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.
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- Thank you! This was exactly what I needed to do.
One thing I noticed when performing the conversion during an upgrade task sequence, you will lose the ability to "rollback" to previous build of Windows 10. This makes sense but I didn't see it documented anywhere.
Usama MustafaMicrosoft
is it necessary to have Creators update to execute mbr2gpt command?
It's necessary to have Creators Update if you wish to run the tool from within Windows (Full OS). MBR2GPT does support older versions of Windows 10 when ran from the WinPE thats included in Windows ADK 1703.
- 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. - Yes! Because that tool is only available for that version and after versions.
- I get this error when trying to do the /validate
ValidateLayout: Wrong boot partition count, expected 1 but found 0.
Any idea why that is?- Just from the look of the error, it sounds like it cannot find a boot partition. How are you running the command?
mbr2gpt /disk:1 /validate
I have tried from both WinPe and within Windows.
This is the full transcript for the command prompt.
C:\Windows\system32>mbr2gpt /disk:1 /validate /allowfullos /logs:c:\temp MBR2GPT: Attempting to validate disk 1 MBR2GPT: Retrieving layout of disk MBR2GPT: Validating layout, disk sector size is: 512 bytes Disk layout validation failed for disk 1
hi
i tried to convert from mbr to gpt using the cmd
my widows builed is 1703
when i enterd the command to validate the disk
this is the message that i got
can you please help me to know what is wrong
my laptop allow for uefi
C:\Windows\system32>mbr2gpt /validate /disk:0 /allowfullos
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 0thanks in advanced
- I Had the same error while trying to convert my mbr hard disk to gpt.
what I did for getting success was the following:
1.- checking my partitions in computer management, I saw my two partitions (system reserved and OS ) were primary partitions, but data partition Or D: (as I use to call it) was in logical partition state.
2.- I installed Minitool Partition Wizard and converted logical partition to primary.
3.- Run into windows Enviroment the mbr2gpt /convert /disk:"number of the disk" /allowFullOS and the... IT WORKED!
Hope you Found this helpful.
Error while validating Disk
C:\WINDOWS\system32>mbr2gpt /allowFullOS /validate
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- hi, if mbr disk have 4 partitions it will fail, i deleted one partition then it worked.
- 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.
Check your setupact.log & setuperr.log files in %Windir%\Panther. There should be some verbose information in one of those logs.
-Mike
Does this work for Home or Pro versions of Windows 10? Or just enterprise?
- Pro working, so home must work too.
- I accidentally deleted the MSR partition from the drive when downloading Windows. Should I recreate the MSR? If so, does anyone know how to do it?
Tried a lot.
I am getting an "unrecognized partition error".
This 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 overviewMBR2GPT validation and result
- Use third party tool to convert the logical partition to primary partition
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
