[SOLVED] Need help to convert system disk to GPT for UEFI boot without losing data

baboo85

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Hi all, I have a particular problem.My PC was a single partition Windows 7 upgraded to Windows 10.

I have a single system partition and another one with data. I can't convert to GPT disk, nor with mbr2gpt command (in Windows or using a bootable usb), nor with tools like AOMEI Partition Assistant.

With the mbr2gpt command I have a "Disk layout validation failed" error and with AOMEI if I convert to GPT it causes an error and it convert the disk to GPT deleting all partitions (thank god I can go back re-converting to MBR and restoring partition).

Doing the shrink volume trick with 200MB and 2GB on both partition, the mbr2gpt returns "Cannot find OS partition(s) for disk 0". Funny, because I can boot the PC and I'm writing this post on this PC right now.

I'm almost 100% sure that the problem is that I have no boot nor recovery partition because when I installed Windows 7 i created only one partition and the boot information are on the first partition (I have boot and recovery folder under C:\ with all the needed files).

I also tried to use bootrec commands but with no success (even with creating a FAT32 500MB partition, the bootrec /fixboot command return the Access Denied error and I can't recover from it with bcd command).


There is any way to fix this problem? I need to convert this disk to GPT so I can boot in UEFI mode, I just need that. Obviously without losing data, I wouldn't be here otherwise...
 
Have to say - all those questions were valid. People not always have a proper idea, how to achieve their intended result the best way.

Here was issue similar to yours resolved.

Note - if you're upgrading to a new computer, then only proper way of migrating is clean OS install - not cloning and not moving OS drive to the new pc.
Trying to avoid this introduces several problems.
 
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baboo85

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1) I think this is the hilarious question to ask in a forum/site on a technical help request.
Other than the fact that I already said that at the end of the post, I'll answer.

I need to convert my disk to GPT to boot into UEFI mode. And this is a fact, you can't have MBR disk to boot into UEFI.
To be more specific (and to avoid the "why you need to boot into UEFI mode), I'll say that legacy/bios boot is old as heck, and modern systems don't even have legacy boot, and I want to clone my old system to a new one, that doesn't support legacy/bios boot.

Still, that was an hilarious question. I imagined going to a repair shop or a mechanic asking for help, and dude asks why I need help. LOL.

2) Extremely false. Even Windows has the mbr2gpt command to mantain all data and third party partition softwares have it. And it's an easy and instant command (if you have all green lights when using the /validate option).

3) Not necessary anymore, I solved it. I'll post how I did it, I need to recap the right things I did because I've done a lot and the next problem I'm facing it's so difficult that it's almost impossible, and I'm messing around with many things.
 
Have to say - all those questions were valid. People not always have a proper idea, how to achieve their intended result the best way.

Here was issue similar to yours resolved.

Note - if you're upgrading to a new computer, then only proper way of migrating is clean OS install - not cloning and not moving OS drive to the new pc.
Trying to avoid this introduces several problems.
 
Reactions: baboo85

baboo85

Reputable
Nov 6, 2017
16
1
4,515
1
Have to say - all those questions were valid. People not always have a proper idea, how to achieve their intended result the best way.
No, depends on the question asked. Also I already stated in the first post that I need to boot into UEFI mode, and I think this is absolutely obvious why I need it. Bios/legacy boot with an MBR disks is too obsolete.

Note - if you're upgrading to a new computer, then only proper way of migrating is clean OS install - not cloning and not moving OS drive to the new pc.
Trying to avoid this introduces several problems.
Again, no. This answer is what enrage me so much in forums and is the standard answer in the "answer microsoft" site.
If I'm doing this is because I DON'T WANT to do a clean OS install, otherwise I wasn't here to ask for help.

This answer reminds me an old problem, bought Windows 8 upgrade from Windows 7 system, asking for help because the upgrade fails, they answered me "do a clean OS install". Really? I BOUGHT the UPGRADE because I wanted to mantain all, and they told me to o a clean OS install. WTF...
Anyway I solved that without their useless help (really, answer microsoft is the worst site).

Here was issue similar to yours resolved.
Well, this is nice and I would have hoped to find this some days ago. That's pretty much what I did, but didn't find it before.
I don't need to explain what I did, that's all the things to do (I used different parameters with bcdboot but the result is the same).

Well, thank you anyway for reporting that thread to me, I should have asked this before.
 

USAFRet

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Mar 16, 2013
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1) I think this is the hilarious question to ask in a forum/site on a technical help request.
Other than the fact that I already said that at the end of the post, I'll answer.

I need to convert my disk to GPT to boot into UEFI mode. And this is a fact, you can't have MBR disk to boot into UEFI.
To be more specific (and to avoid the "why you need to boot into UEFI mode), I'll say that legacy/bios boot is old as heck, and modern systems don't even have legacy boot, and I want to clone my old system to a new one, that doesn't support legacy/bios boot.

Still, that was an hilarious question. I imagined going to a repair shop or a mechanic asking for help, and dude asks why I need help. LOL.

2) Extremely false. Even Windows has the mbr2gpt command to mantain all data and third party partition softwares have it. And it's an easy and instant command (if you have all green lights when using the /validate option).

3) Not necessary anymore, I solved it. I'll post how I did it, I need to recap the right things I did because I've done a lot and the next problem I'm facing it's so difficult that it's almost impossible, and I'm messing around with many things.
1. I asked, because different 'reasons' can lead to vastly different answers.

2. A good backup is strongly recommended, because things happen.
MBR2GPT usually works just fine. Usually.
Sometimes, the cause of a fail is out of our control.
I would never embark on a potentially data destructive procedure like this without a known good backup. Just in case.

3. Glad you got it working. Good luck.
 
MBR2GPT usually works just fine. Usually.
Sometimes, the cause of a fail is out of our control.
There are certain requirements for mbr2gpt to work. They are not secret.

Disk Prerequisites
Before any change to the disk is made, MBR2GPT validates the layout and geometry of the selected disk to ensure that:
  • The disk is currently using MBR
  • There is enough space not occupied by partitions to store the primary and secondary GPTs:
    • 16KB + 2 sectors at the front of the disk
    • 16KB + 1 sector at the end of the disk
  • There are at most 3 primary partitions in the MBR partition table
  • One of the partitions is set as active and is the system partition
  • The disk does not have any extended/logical partition
  • The BCD store on the system partition contains a default OS entry pointing to an OS partition
  • The volume IDs can be retrieved for each volume which has a drive letter assigned
  • All partitions on the disk are of MBR types recognized by Windows or has a mapping specified using the /map command-line option
If any of these checks fails, the conversion will not proceed and an error will be returned.
https://docs.microsoft.com/en-us/windows/deployment/mbr-to-gpt
 

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