Converting Windows 10 from GPT to MBR, and restore using Acronis

Please do not answer this unless you know EXACTLY what you are talking about; guesses and partial answers and theories are not appreciated on this one.

I have Windows 10 installed on my Lenovo laptop.  The Disk is GPT.  I want to convert to MBR, even though this is generally considered a "downgrade".

Per the Windows Disk Management utility, there are several partitions, as follows:

(hidden) 1000MB Recovery Partition
(hidden) 260MB EFI System Partition
(hidden) 1000MB OEM Partition
C: 890GB System partition (Boot, Page File, Crash Dump, Primary Partition)
D: 25GB NTFS Primary partiton
(hidden) 14GB Recovery Partition

I would like to back everything up using Acronis Truimage 2016, use diskpart to wipe the drive and convert it to MBR, and then bring back only what I need to bring back, and have it be bootable.

I don't particularly need the recovery partitions, as I've created an installer thumbdrive for the OS.

So, specifically:  Do I need to change anything in the laptop's BIOS (like change UEFI to Legacy)?  If so, at what point in the process would I do this?
Do I need to restore the EFI System partition if the disk will be MBR rather than GPT?
If, using Acronis, I just restore C: and D:, do I need to do anything in particular so that it will boot from C: when I'm done?  For example, make the partition active, or primary?
I suspect that Acronis will back up and restore a master boot record.
Will Acronis figure out that the master boot record needs to say to boot from C:, and make the necessary changes to it?  Or do I need to do something in particular to ensure that I will be able to boot from C: after the restore?

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JohnBusiness Consultant (Owner)Commented:
The only question I can answer is the first one. To convert to MBR from GPT, you MUST convert UEFI to Legacy. That is for sure. UEFI requires GPT.

So then can you convert from UEFI to Legacy in Windows 8.1 or Windows 10? Everything I read says NO.
David Johnson, CD, MVPOwnerCommented:
Actually you can but it requires a bit of work
see my youtube video. I used server 2012R2 but the principles still apply
akahanAuthor Commented:
David, as far as I can tell from your video, your method requires a virtual machine, and that the disk being converted isn't the only disk in the machine... in other words, you need another disk from which to run the utilities.  Do I have that wrong?  Or is it possible to do what you did with a single drive, and no virtual machine?
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JohnBusiness Consultant (Owner)Commented:
That is what I thought and I am not at all sure you can convert a UEFI BIOS to Legacy. You would have to do this as a first step if you can do it at all (reference your overall question).
akahanAuthor Commented:
The BIOS on my Lenovo allows you to select UEFI or legacy...It's just not clear to me exactly when in the backup/restore process would be the right time to do it... (along with my many other questions...)
JohnBusiness Consultant (Owner)Commented:
UEFI requires GPT disk. Legacy BIOS can run GPT or MBR (I am fairly sure of that). So then convert to Legacy BIOS and then convert the disk.

Back it all up first so that you can restore the computer if you need to.
JohnBusiness Consultant (Owner)Commented:
What I am not sure about is converting to Legacy with Windows 10 (or Windows 8.1) installed. You could do it with Windows 7.
akahanAuthor Commented:
Right, that is one of my concerns, exactly.  It may be that I will have to wipe the disk, convert to MBR, and reinstall Windows 10 from scratch, and then <sigh> re-create all the configuration I have spent the last month or so doing to get Windows 10 to behave as i would like, reinstall all my apps, transfer my data back... yuck.   Really hoping to avoid all that!
JohnBusiness Consultant (Owner)Commented:
You might be lucky.

I have a Lenovo ThinkPad. It came with Legacy BIOS and Windows 8. When I upgraded to Windows 8.1, I know it converted to UEFI BIOS. It told me that on the way through. I thought I recalled it saying it was a one way street. But the above article suggests you might get away with going backward.
akahanAuthor Commented:
Right, the distinction is:  Certainly you can install Windows 10 *fresh* on a legacy machine.  The question is whether you can back up a Windows 10 system partition that was created on a UEFI BIOS, change the BIOS to legacy, restore the system partition back, and expect it to boot.  Or, alternatively, whether Windows 10 "knows" it's being installed on a UEFI BIOS, and sets itself up differently for such a BIOS than for a legacy BIOS.
JohnBusiness Consultant (Owner)Commented:
Another approach is to consider a backup alternative which will backup Windows 10 GPT images.

We use Symantec Ghost for Windows 7 to do what you are wanting to do.

Symantec is replacing Ghost with Symantec System Recover 2013 R2 for Windows 8.1. They are working on a patch for Windows 10.

Really, instead of converting your Windows 10 machine to a downgraded way of working (and at the risk of having to rebuild it), consider waiting and using a product built for going forward.
akahanAuthor Commented:
Sorry, I don't think you are understanding the issue here, or what I want to do.

My current backup software (Acronis Truimage 2016) works fine with GPT.  

I want to convert to MBR because I have products that will not run on GPT, and I would like to continue to use those products.
JohnBusiness Consultant (Owner)Commented:
I want to convert to MBR because I have products that will not run on GPT  <-- New information - you had not said this in the original question.

Everything I have on my Windows 10 machine works without issue.

Make a backup of your computer, change the BIOS to legacy and see if it works. The worst that can happen is a complete restore and try again.
noxchoGlobal Support CoordinatorCommented:
The Windows will not work after changing the BIOS settings to Legacy (disabling UEFI).
The Windows will not start after converting the drive into MBR type if you do not perform necessary steps.

Akahan, you can perform the steps described by David from a boot CD of Acronis True Image you have. Does it have on its Boot CD an option to convert the GPT to MBR?
You can there delete the EFI partitions (note, after deleting Recovery Partition which has WinRE you will loose the option to perform automatic repair of Windows).

Then you will need a DVD or USB with Windows 10 installation on it to perform the fixboot and rebuildbcd.
noxchoGlobal Support CoordinatorCommented:
I have performed the operation which you need but used a tool from Paragon - Hard Disk Manager 15 to convert the drive. Plus I used Windows 10 installation DVD to perform rebuildbcd command.
So step by step:
1) Get to BIOS and turn the UEFI Boot off
2) Boot the PC from an Acronis Boot CD (if it has a convert GPT to MBR feature)
3) Convert the drive and delete two partitions. You can even delete the first partition of 450MB but I left it
4) Once done - start the PC from Windows 10 installation media - select Repair - Advanced
5) Enter Dispart and perform the commands I did.
6) Once finished reboot to Windows

Note, the attached file normally has .exe extension. I changed it to EFI2MBR.png so that I could upload it. Download it and change the extension back to exe (EFI2MBR.exe) then double click on the file and it will play the video.

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akahanAuthor Commented:
noxcho, thanks for the clear explanation.  I ended up using Paragon, just as you did, to be safe.   (Acronis Truimage is a backup program, and not really a partition manager.  Its bootable rescue disk will INITIALIZE disks in GPT or MBR, as you choose, but as far as I can tell cannot convert one to the other.)

The conversion was exactly as you described, went perfectly, and my programs that are incompatible with GPT now work.  Thanks for your help!
noxchoGlobal Support CoordinatorCommented:
Thanks for feedback. Glad to be helpful.
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