Question SSD not booting after recreating bootloader following failed MBR/GPT conversion

[Domino00]

Hi all, I needed to enable secure boot after a GPT conversion via the CMD prompt but it appears the conversion failed (no asterisk under "GPT" in the diskpart in the attached pic). It wouldn't boot to the OS so I attempted to recreate the bootloader following the steps here to no avail.

I can only boot to the Windows 10 repair USB otherwise I get an "OS not found on the partition" message. Can anyone advise? Thank you.

 

[SkyNetRising]

Execute this:

bootsect /nt60 C: /force​

C: - here is 500MB bootloader partition.
If bootloader partition has a different drive letter, then change accordingly.

Make sure CSM is enabled.

 

[Domino00]

@SkyNetRising Thanks for the reply. CSM is enabled.

 

[SkyNetRising]

@SkyNetRising Thanks for the reply. CSM is enabled.

Wrong syntax.
There has to be space symbol between "C:" and "/force"

bootsect /nt60 C: /force​

 

[Domino00]

My fault. It executed but still receiving an error that an OS was not found.

 

[SkyNetRising]

Well?
Are you able to boot into windows now?

 

[Domino00]

Unfortunately no. Still getting the same message above when booting..."OS not found".

 

[SkyNetRising]

Can you show screenshots from BIOS

Boot Priority settings,​

Hard Drive BBS settings.​

​

Note - CSM has to be enabled. Check that too.

 

[Domino00]

 

[SkyNetRising]

Storage Boot Option control - set to legacy.
Other PCI devices - set to legacy.

 

[Domino00]

Changed. OS still not found.

 

[SkyNetRising]

You said - you tried to do conversion and it failed.
May be failure has left your drive in some weird state.

Try to redo conversion.
Confirm OS disk number first. Should be Disk 0.

diskpart​

list disk​

exit​

Validate, if conversion requirements are met.

mbr2gpt /validate /disk:0​

If successful, then proceed with convert.

mbr2gpt /convert /disk:0​

Show screenshots.

 

[Domino00]

Nothing on either disk 0 or 1

 

[SkyNetRising]

Interesting.
It says, it can't find OS partition.
May be mbr2gpt expects bootloader and windows partitions be in specific order on disk.
Usually bootloader is before windows partition.
Did you delete old 100MB bootloader partition? There is 100MB unallocated on disk.

Lets try this way.

diskpart​

list disk​

select disk 0​

list partition​

create partition primary​

format fs=ntfs quick​

active​

assign letter=H​

list volume​

(note drive letter for windows partition 931GB. Was E: in your previous screenshots)​

exit​

bcdboot E:\windows /s H:​

(replace E: with appropriate letter for windows partition)​

bootsect /nt60 /all /force​

(show screenshots)

​

Reboot and try to load into windows.

If still no success, then redo instructions from post #12.
(show screenshots)

 

[Domino00]

I haven't deleted any partitions. I made an error and had to go back to create the 100MB new partition, which is on C: and the Windows partition is still on E. Bootsect was unsuccessful though still no OS and validation failed.

 

[SkyNetRising]

Error in bootsect command syntax.
You entered bootsec instead of bootsect.

bootsect /nt60 /all /force​

Conversion command did not say - can not find OS partition.
Delete 500MB and 584MB partitions

diskpart​

list disk​

selct disk 0​

list partition​

select partition 4​

delete partition override​

select partition 3​

delete partition override​

exit​

Try conversion after that.
Validate.

mbr2gpt /validate /disk:0​

Convert.

mbr2gpt /convert /disk:0​

Show screenshots.

 

[Domino00]

Started over and deleted the 100MB partition and also made a correction to the bootsect syntax "ALL" vs "/ALL". Still not loading and disk 0 will not validate.

 

[SkyNetRising]

And it still doesn't boot?

Try conversion even, if validation says it failed.