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When trying to convert to GPT, I get this error:

PS 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 0

Here's diskpart info:

PS C:\WINDOWS\system32> diskpart

Microsoft DiskPart version 10.0.17134.1

Copyright (C) Microsoft Corporation.
On computer: DESKTOP-74HKFD4

DISKPART> list disk

  Disk ###  Status         Size     Free     Dyn  Gpt
  --------  -------------  -------  -------  ---  ---
  Disk 0    Online         2794 GB      0 B

DISKPART> sel disk 0

Disk 0 is now the selected disk.

DISKPART> list part

  Partition ###  Type              Size     Offset
  -------------  ----------------  -------  -------
  Partition 1    Primary            500 MB  1024 KB
  Partition 2    Primary            519 GB   501 MB
  Partition 3    Recovery           885 MB   520 GB
  Partition 4    Primary           1525 GB   521 GB

And here's a picture of disk management:

Disk Management

I've tried shrinking the storage by a few GB in case it was the issue, but no luck. I'm kinda out of ideas. Maybe the recovery partition counts as a primary partition and thus I go over the 3 primary maximum? It shouldn't, but that's the only idea I have left.

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  • 4
    One of mbr2gpt's requirements is that "There are at most 3 primary partitions in the MBR partition table". You have 4, therefore you can't do the conversion with the built-in tool. Use a 3rd party one instead, or delete the recovery partition Cannot convert from MBR to GPT – phuclv Dec 16 '18 at 10:08
  • Well, thanks for the help, I'll try a 3rd party tool for this. As I said in my post, I was confused because all of the info online I found said the limit is 3 primary partitions, and it quite specifically says that the recovery partition made by windows is not a primary partition. – Niko Matikainen Dec 16 '18 at 11:58
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    All of the programs mentioned there require a pro version to do this conversion, so I just got rid of my recovery partition. I don't need it anyways since I have installation media available if I ever need to reset to a blank W10. Now it worked, and I finally managed to put that 746GB to use on my storage partition. :) – Niko Matikainen Dec 16 '18 at 12:17
  • just open a real disk partitioning tool to see whether it's primary or logical. I'm quite certain that it's a primary one since Windows never creates a logical partition for its use, and the extended partition is often the last one in the list. However since I don't have an MBR system for a long time I can't verify it – phuclv Dec 16 '18 at 12:34
  • Well, I think it was also mentioned that logical and extended partitions also prevent the conversion, so the result would be the same in any case. – Niko Matikainen Dec 16 '18 at 15:34
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UUmmmm. I don't believe it is possible if the MBR drive has multiple partitions. If it was one BIG drive partition then yes, it would work. You might be able to merge your partitions without data loss using a 3rd party software such as Easeus or something similar but I wouldn't try that without backing up your data first.

Someone else please correct me if I am wrong here but an MBR drive with multiple partitions cannot be converted to GPT partitioning without data loss and re-installation of the OS.

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  • what makes you think it can't? MBR has 4 partition entries, so it can contain 4 primary partitions, or 3 primary + 1 extended (which is used to host logical drives). And multiple partitions cannot be converted to GPT partitioning without data loss and re-installation of the OS is wrong. There are a lot of 3rd party tools that can do the conversion without loss – phuclv Dec 16 '18 at 10:04
  • Welcome to Super User. Why don't you believe it's possible? Any technical explanation? reasoning? source? Well, I believe it's possible, unless there's no space for primary or secondary GPT; and in this case it appears there is space. Other constraints (e.g. a bootloader stage that resides outside the partitioned space) may be reasons not to do it, but the new partition table and partitions themselves, filesystems and data therein should be fine with GPT scheme. – Kamil Maciorowski Dec 16 '18 at 10:07
  • UUmmm - thats why I said "correct me if I am wrong", I wasn't sure if 3rd party tools could do it with multiple partitions. – Jatmin Dec 16 '18 at 10:29
  • I guess it's a little late now but you could've used a linuxmint boot disk and/or a gparted boot disk which both contain the "gdisk" application. – Jatmin Dec 17 '18 at 19:29

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