Windows 10: Convert Windows 10 from Legacy BIOS to UEFI without Data Loss

Matter solved, thanks!

FWIW ...

[Screenshot 1]
From admin command prompt

mbr2gpt /validate /allowFullOS

and then:

mbr2gpt /convert /allowfullOS






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[Screenshot 2]
From admin command prompt

Diskpart
List Disk

shows the converted drive (disk 1)





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[Screenshot 3]
Run msinfo32
shows that now UEFI is enabled to boot from.





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[Screenshot 4]
run dskmgmt
before and after - shows an extra partition





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[Screenshot 5]
Motherboard BIOS (Asus X99 DeLuxe/U3.1)
select Boot section in BIOS
select CSM
select Enabled
select UEFI and legacy OpROM

'Enabled' and 'UEFI and legacy OpROM' were already selected in my case)
(tried UEFI only, but that disables the keyboard)




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Small note:
In my case the steps outlined in "How to Boot to UEFI Firmware Settings from inside Windows 10" didn't work.
Start->Settings->Update & Security->Recovery->Restart Now (Advanced Startup)->Troubleshoot->Advanced Options...

from this point on Windows restarted ("Please Wait" and "Turning off your computer"), instead of 'Startup settings",
instead of getting "UEFI Firmware Settings".

Anyway, matter solved.

 

Great news tfwul. *Party

 

For clarity, you can only change UEFI settings if already booted to UEFI. If booted as legacy bios, that option does not exist.

 

It's about time Windows included this tool. Worked perfectly for me. I was searching the internet for a way to do this without having to wipe my OS drive and re-partition or purchasing a pro version of a partitioning tool.

 

It was not that difficult to do. You basically had to image backup current C drive, then clean install Windows 10 as UEFI, then restore image overwriting c drive, making sure you had all the right files in c:\windows\boot directory (I copy that directory from clean install to a backup drive just in case). However, no need to do that anymore if running 1703.

 

Not difficult, but time consuming. Took less than a few minutes to run mbr2gpt, reboot, and change bios to UEFI.

 

Sure but mbr2gpt only works with W10 version 1703. You can use a 1703 installtion drive though to convert older versions.

 

I realize it's recommended to install a new OS when changing mainboards rather than keeping your current installation and just installing new drivers, but I've done it before and intend to do it again.

I can't see why adding a BIOS to UEFI conversion to the mix would be problematic, but has anyone tried this before? Should just be a matter of running the conversion, then swapping out CPU/mainboard/RAM, then booting up the new rig in UEFI.

 

Hello Ralphus, and welcome to Ten Forums. *Smile

As long as everything in the red warning box at the top of the tutorial checks out ok, you shouldn't have any issues converting to UEFI.

Of course, I would always recommend to back up anything that you do not want to lose first to be extra safe.

 

Thanks for the welcome, and the reassurance. *Smile

 

Thanks, works fine with an Intel 600P 256GB m.2 SSD Windows 10 1703 with Asus Prime B250 Plus motherboard 0808 bios.

 

Wishing I hadnt tried this, now wont boot. Had a perfectly good running ASUS K60IJ, am hoping someone can help. I could not find the uefi option in the bios. Cant boot from windows 10 or linux flash drive either. After the splash screen all i see is in the attachment.

 

Hello @DaLee, and welcome to Ten Forums. *Smile

Check to see if you may have a "CSM" type setting instead to disable in your UEFI firmware settings.

 

Thanks for responding Brink. Looks as if this PC does not have uefi firmware settings only bios, came with windows 7 originally. Was finally able to figure how to boot from flash drive at a cold boot after changeing a few settings in bios and video taping the display to catch the text on the screen as it flew by. *Huh

Is there a chance of a bios upgrade that may give the uefi option needed? Am looking now for newer version, wasnt any during the free W10 update. Currently has AMIBIOS Version 206

In a worst case scenario would a fresh install get me back to mbr ok?

Would there be a command prompt to revert back without losing data?

Or does this not work at all...
Convert GPT drive into MBR using Command Prompt (cmd).

 

Odd. If your hardware didn't support UEFI, the conversion should have failed during the check to prevent it from being converted.