[SOLVED] PC wont boot after doing mbr2gpt convert using third party software

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Nov 30, 2022
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Hi All,

I hope you can help me, so i have a custom built gaming pc i had built when i was at university in 2020 and i will list the specs i remember or can see as i now do not have access to my uni email account where i had the email with the full specs in.

I have:

Windows 10 Home operating system
Gigabyte H310M S2H 2.0 Motherboard
Intel i5 Processor
32GB DDR4 Ram
512GB Western Digital PC SN730 NVMe SSD
Gigabyte GeForce® GTX 1660 OC 6G Graphics Card
500w PSU (I think its 500w or maybe 550w??)

So what i was trying to do was get my PC ready so i could upgrade to Windows 11, and to do that i had to change two main things, with the first being to enable TPM which i did successfully within BIOS by enabling Intel platform trust technology (PPT). After this i needed to do the mbr2gpt convert so as to enable secure boot, which i used available software which claims to be able to do the convert whilst still logged into windows 10. Before attempting the convert i deleted the recovery partition as you cannot do the convert if you have more than 3 separate partitions shown in Disk Management Console. I started the convert but got an error message which i cannot remember what it said but I'm sure it was an exceptional error code with lots of numbers, i know, i know, that's no help whatsoever lol.

I was still logged into windows and still able to use everything as normal until i restarted the PC as It said i needed to restart the pc which is what i did and that's when i got the boot error message 'A disk read error occurred press Ctrl+Alt+Del to restart' after the BIOS selection screen (i.e press F12 to enter bla bla bla).

I looked for a possible solution online which is when i found the below information:

Boot from Windows installation media into command prompt mode.
Execute these and show command output
(upload screenshot to imgur.com and post link)

diskpart
list disk
select disk 0
list partition
list volume


If you have more than one disk, then also list partitions of remaining disks
select disk 1
list partition
select disk 2
list partition


Now when i type that in command prompt using a recovery media usb so i can access Command Prompt i can see the partitions on my SSD however i cant boot into windows. This is a link to pic of my results using the above commands:

View: https://imgur.com/a/DVkUswW



Let me know if you need any further in for etc,

Thanks in advance

Mark
 
Solution
Screenshots below:
Bootloader partition is too small. Only 50MB. Recommended size is 350MB - 500MB.
bcdboot command is failing because of this.
You'll have to create a new bootloader.
Execute following and show screenshot.
If you get any errors, then stop immediately.
diskpart
list disk
select disk 0
list partition
select partition 3
shrink desired=500
create partition primary size=500
format fs=ntfs quick
active
assign letter=H
exit
bcdboot E:\windows /s H: /v
should i do anything else now im in to rectiify anything or fix the system files etc?
You should delete 50MB system reserved partition.
That is old bootloader. No longer necessary.

After that you could try converting OS drive to UEFI compatible again with mbr2gpt.
Validate first.
mbr2gpt /validate /disk:0 /allowfullos
If validation is successful, then proceed with conversion.
mbr2gpt /convert /disk:0 /allowfullos
Then boot into BIOS and set first boot device to Windows Boot Manager.
 
Last edited:
Nov 30, 2022
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You should delete 50MB system reserved partition.
That is old bootloader. No longer necessary.

After that you could try converting OS drive to UEFI compatible again with mbr2gpt.
Validate first.
mbr2gpt /validate /disk:0 /allowfullos
If validation is successful, then proceed with conversion.
mbr2gpt /convert /disk:0 /allowfullos
Then boot into BIOS and set first boot device to Windows Boot Manager.

Should i delete the 50mb partition via command prompt or can i do it in disk management
 
Nov 30, 2022
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You should delete 50MB system reserved partition.
That is old bootloader. No longer necessary.

After that you could try converting OS drive to UEFI compatible again with mbr2gpt.
Validate first.
mbr2gpt /validate /disk:0 /allowfullos
If validation is successful, then proceed with conversion.
mbr2gpt /convert /disk:0 /allowfullos
Then boot into BIOS and set first boot device to Windows Boot Manager.

Ive just deleted the 50mb partition, can i reallocate that 50mb to another partition and if so how do i do it as in disk management i cant seem to add it to any other, and i cant stretch any other partition. When i try the above mbr2gpt command, should i do that when logged into windows or should i enter command prompt by restarting into recovery console?
 
Ive just deleted the 50mb partition, can i reallocate that 50mb to another partition and if so how do i do it as in disk management i cant seem to add it to any other, and i cant stretch any other partition.
No. If you try to rearrange partitions to add those unused 50MB, you have a high chance of messing everything up to point of full reinstall.
Just leave it.
When i try the above mbr2gpt command, should i do that when logged into windows or should i enter command prompt by restarting into recovery console?
With /allowfullOS switch you can run from within windows.
Without /allowfullOS switch you can run it from recovery console only.
 
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Nov 30, 2022
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You should delete 50MB system reserved partition.
That is old bootloader. No longer necessary.

After that you could try converting OS drive to UEFI compatible again with mbr2gpt.
Validate first.
mbr2gpt /validate /disk:0 /allowfullos
If validation is successful, then proceed with conversion.
mbr2gpt /convert /disk:0 /allowfullos
Then boot into BIOS and set first boot device to Windows Boot Manager.

I did the convert and got the following failed to update, is that something i need to do anything about?

C:\windows\system32>mbr2gpt /convert /disk:0 /allowfullos

MBR2GPT will now attempt to convert disk 0.
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
MBR2GPT: Migrating default boot entry
MBR2GPT: Fixing drive letter mapping
MBR2GPT: Conversion completed successfully
Call WinReReapir to repair WinRE
MBR2GPT: Failed to update ReAgent.xml, please try to manually disable and enable WinRE.
MBR2GPT: Before the new system can boot properly you need to switch the firmware to boot to UEFI mode!
 
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Did you run it from elevated command prompt?

Anyway - recovery environment is not essential.
You can get all the functionality from it just by booting from windows installation media.

yes i did run as administrator, ok no worries, should i re run the convert command or just move straight on to change the first boot device in the BIOS
 
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Nov 30, 2022
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Windows 8/10 Features -> Other OS. Save and Reboot.
UEFI options should appear.

If still no UEFI options, then set CSM to disabled.

ok so UEFI didnt appear in first boot after selecting 'other OS' and rebooting, so i have set CSM to disabled and have the options below in BIOS. If you look in the above picture UEFI is selected for 'Storage boot option control' and for 'other PCI devices' is that relevant?

View: https://imgur.com/a/LBWwChD
 
Nov 30, 2022
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Windows 8/10 Features -> Other OS. Save and Reboot.
UEFI options should appear.

If still no UEFI options, then set CSM to disabled.

sorry to bother you but i was just wondering about the above last few posts, as atm im still in BIOS waiting for what do do next, i dont mean to sound inpatient, as im very appreciative for your help
 
should i enable secure boot as that is one of the windows 11 upgrade requirements?
No. Do not touch secure boot just yet.
You have to make it able to boot in UEFI mode first.
See, what options are available at Save& Exit/Boot Override.
Do you see any UEFI options?
Try loading optimized defaults (BIOS/Save&Exit)

It may be necessary to recreate UEFI bootloader.
Boot from windows installation media. And show screenshot.
diskpart
list disk
select disk 0
list partition
list volume
 
Nov 30, 2022
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No. Do not touch secure boot just yet.
You have to make it able to boot in UEFI mode first.
See, what options are available at Save& Exit/Boot Override.
Do you see any UEFI options?
Try loading optimized defaults (BIOS/Save&Exit)

It may be necessary to recreate UEFI bootloader.
Boot from windows installation media. And show screenshot.
diskpart
list disk
select disk 0
list partition
list volume

When looking at 'Save& Exit/Boot Override' it is basically greyed out so wont allow me to select it. Other options are:

Under 'BIOS'

Boot configuration: Bootup Numlock State - ON
Storage Boot Option Control - Set to UEFI (Other choices are 'Do not launch'/'Legacy'/'UEFI')
Other PCI Devices - Set to UEFI (Other choices are 'Do not launch'/'Legacy'/'UEFI')

Under 'Peripherals'

Intel Platform Trust Technology (PPT) - Disabled


Under 'Save & Exit'

Boot Override - Only available option is WDC PC SN730 SDBPNTY-512G-1032
 
Nov 30, 2022
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No. Do not touch secure boot just yet.
You have to make it able to boot in UEFI mode first.
See, what options are available at Save& Exit/Boot Override.
Do you see any UEFI options?
Try loading optimized defaults (BIOS/Save&Exit)

It may be necessary to recreate UEFI bootloader.
Boot from windows installation media. And show screenshot.
diskpart
list disk
select disk 0
list partition
list volume
View: https://imgur.com/a/nPKqVM1
 
Then recreate EFI bootloader.
If you get any errors then stop immediately.
diskpart
list disk
select disk 0
list partition
select partition 4
(select 500MB primary partition - old legacy bootloader)​
delete partition
list partition
select partition 2
(select 100MB System partition)​
delete partition override
create partition efi size=500
format fs=fat32 quick
assign letter=H
exit
bcdboot C:\windows /s H: /f UEFI /v
Last message should be "Boot files created successfully".
Show command output.
 
Nov 30, 2022
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Then recreate EFI bootloader.
If you get any errors then stop immediately.
diskpart
list disk
select disk 0
list partition
select partition 4
(select 500MB primary partition - old legacy bootloader)​
delete partition
list partition
select partition 2
(select 100MB System partition)​
delete partition override
create partition efi size=500
format fs=fat32 quick
assign letter=H
exit
bcdboot C:\windows /s H: /f UEFI /v
Last message should be "Boot files created successfully".
Show command output.
View: https://imgur.com/a/eWHw5X5