Upgrading from Windows 10 (Legacy) to Windows 10/11 (UEFI)

I'm looking for a solution for a client to upgrade one of their Window 10 devices. The Windows 10 machine is booting Legacy. It works but have noticed some flakiness. I don't want to make any changes to the machine as I need it to keep working.


I want to move to a new machine ( Dell ) that only supports UEFI boot. It comes with Windows 11 but I would be just as happy having Windows 10 on new device.


I have a licensed version of Macrium. I was thinking of restoring just the C: drive to the new device but wasn't sure if the BCD Store would accept this and boot.


I can't start fresh on the new machine with installing software as it would be a nightmare and there are many settings and printers that the user says were set up special.


Has anyone transplanted a Legacy Windows 10 on to a machine that boots UEFI? Any recommendations / advise?

Really appreciate any help.

As an added complexity the edition / version of Windows 10 on old device is Home/latest patch level. The new machine is licensed 11 Pro so I may have to upgrade original license to pro.

@Caledon Ken


You can covert MBR to GPT without data loss.
You will have to do this before or after you clone or move a backup.

Once done, you will have to set Secure Boot to UEFI or UEFI and Legacy, or the newly converted disk won't boot.

Convert Windows 10 from Legacy BIOS to UEFI without Data Loss



Also... the Macrium bootable Rescue Media has a "Fix Boot problems" tool...
And... you have access to command prompt in lower left corner.

Preserving the original disk is a priority here. Any work you do should be on a clone of that for obvious reasons..

It would be wise to do basic integrity checks on the clone before attempting conversion.

Presumably the old machine is running 64 bit Windows.

There are plenty of threads on this conversion where people have run into minor (?) problems- worth researching.

Caledon Ken said:

I want to move to a new machine ( Dell ) that only supports UEFI boot. It comes with Windows 11 but I would be just as happy having Windows 10 on new device.
I have a licensed version of Macrium. I was thinking of restoring just the C: drive to the new device but wasn't sure if the BCD Store would accept this and boot.....
....Has anyone transplanted a Legacy Windows 10 on to a machine that boots UEFI? Any recommendations / advise?

Yes, I have.

I transplanted my Legacy/MBR System One below to my UEFI/GPT System One over on Eleven Forums, in readiness for its Windows 10 to get offered the Windows 11 upgrade. You're on the right track, you just restore the C: partition.

I wanted to make sure all the EFI partitions were set up correctly, so my first step was to clean install the same version of Windows 10 on the UEFI machine. The next step was, as you say, to restore JUST the C: partition from the old machine's image, replacing the one created by the clean install (and resizing during restore, if required).

As for the BCD, the final step was to use the Reflect rescue media's 'Fix Windows Boot Problems' tool to create a working BCD.

At first boot Windows set up the new drivers, then rebooted into my old familiar desktop with all my installed apps working as before.

I actually did a test migration and ran it for 3 months before the official release, upgrading to 11 with the first released Insider build of 22000.51. I ended up in the curious (and possibly untenable) situation of having a licensed copy of Reflect Home on both machines and both with the same licence key. I didn't dare try unlicensing it from either of them in case I lost access to that licence key for good.

At the end of September 2021 the time came to wipe the test run and repeat the Windows 10 migration for the last time. I took care to remove the Reflect key from the old one before making the image, then reinstalled Reflect on the new one, transferring my key to it.

I was thinking of restoring just the C: drive to the new device but wasn't sure if the BCD Store would accept this and boot.

It does if you don't change the partition or offset.

I often just format ( not delete ) an existing os partition and apply image contents to that partition.

There is a simple workaround to avoid proprietary image programs from making unwanted changes.

mount the image of the partition and then copy the contents of the mounted image to the physical target partition.

the existing win11 bootgfw.efi should boot win 10

It doesnt matter if the old win10 was legacy, the bootmgfw.efi will follow bcd instructions and load winload.efi in win10 system32

you might want to export the drivers from win11 system first.

Thank you all for the info. I'm feeling more confident.


I guess I should have made the reason for this move clearer. The machine I'm now wanting to replace occasionally just goes black and requires a reboot. The machine is 2008/2009 vintage so my thinking is this machine is going to die even if I spend time fixing. Parts are only available on the used market.

I figure better to cross this legacy / uefi bridge when I can stroll across rather than when panic has set in and the device is hard down.

As to my thoughts on Windows 10 / Windows 11. Really I don't care although every potential hiccup, if the machine were on 11, will be blamed on 11. Also while I don't anticipate issues the old software might not play nice with 11. The client is comfortable with 10 so I would prefer to leave it on 10. The next hill I will climb will be the conversion to Windows 11. I have two years to make that journey.


The new machine has the license key, Windows 11 Pro, in the UEFI. I saw your comment @NavyLCDR, and if I read it correctly, I just key in the generic key you provided.