Question Computer no longer boots into Windows 10, need help and advice

[stlcardinalsfan]

I tried using MBR2GPT on my Windows 10 Professional computer. It errored out somehow. I did not catch the error. But now the computer will not boot at all. It says there is no operating system. I would like to go back to a MBR drive and be able to boot into Windows 10 again with a MBR hard drive. Does anyone know how this is done and accomplished? When I try to boot up, it says there is no operating system. MBR2GPT must have done something to the drive, partitions, master boot record, or something else I don't quite understand. I have not been able to find any details on exactly what MBR2GPT does to a hard drive. I do know there are 4 drive letters now that show up in File Explorer. A System Reserved drive letter, my Windows 10 drive letter, and two more drive letters that have no descriptions on what they are. Thanks in advance for your time and help with this.

 

[SkyNetRising]

I would like to go back to a MBR drive and be able to boot into Windows 10 again with a MBR hard drive. Does anyone know how this is done and accomplished?

Depends on, what has been done and when mbr2gpt process errored out.

Boot from windows installation media into command prompt, execute following and show command output:
(upload screenshot to imgur.com and post link)

diskpart​

list disk​

select disk 0​

list partition​

list volume​

I do know there are 4 drive letters now that show up in File Explorer. A System Reserved drive letter, my Windows 10 drive letter, and two more drive letters that have no descriptions on what they are.

How exactly are you seeing that?
Did you connect the drive to another computer?
Can you show screenshot from Disk Management?

 

[stlcardinalsfan]

Yes, indeed. I shall try to do the DOS commands and get the results posted.

Yes, I connected the drive to a working PC. That is where I saw the 4 drive letters in File Explorer and also xplorer2LITE. I will get a screen shot from Disk Management and post that as well.

 

[stlcardinalsfan]

https://imgur.com/a/GbO8vHw

View: https://imgur.com/a/GbO8vHw


Disk Management screen shot of drive that won't boot and gets "No O/S message"

 

[stlcardinalsfan]

https://imgur.com/a/B0n81nC

View: https://imgur.com/a/B0n81nC


Diskpart screen shot of HDD that won't boot and says "No O/S"

 

[stlcardinalsfan]

https://imgur.com/ZGkoLrU

View: https://imgur.com/ZGkoLrU


Disk Management shot of HDD that won't boot and says "No O/S"

 

[SkyNetRising]

Delete partitions I: and J: ,
Set 579MB partition as active,
redo mbr2gpt on the drive.

Show screenshot with the result - command output and Disk Management (full Disk Management window, uncropped).

 

[stlcardinalsfan]

Delete partitions I: and J: ,
Set 579MB partition as active,

I deleted partitions I: and J: and set the 579MB partition as active. SInce I don't want to try to do MBR2GPT again, I tried booting. It gave me an error with the BCD. So I booted up with a Windows 10 disk and did a Repair on the HDD. Lo and behold! It now boots up again to Windows 10 Professional. I'm leaving it there at that and am quite happy to have recovered this. I'll just consider the matter closed. Thanks very, very much for your help, time, and advice! It helped me immensely to get back to where I want to be! Happy, happy, happy!