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

The first step to determine the availability of the recovery partition is to open a command prompt (admin) and run:

reagentc /info

What results do you get?

 

Microsoft Windows [Version 10.0.15063](c) 2017 Microsoft Corporation. All rights reserved.C:\WINDOWS\system32>reagentc /infoWindows Recovery Environment (Windows RE) and system reset configurationInformation: Windows RE status: Disabled Windows RE location: Boot Configuration Data (BCD) identifier: ec7abcc6-1717-11e7-90bf-99e71e99d157 Recovery image location: Recovery image index: 0 Custom image location: Custom image index: 0REAGENTC.EXE: Operation Successful.

 

ok, found the solution:

Create A New Recovery Partition

Note: here we take Windows 8 for example.
Step 1: Download your Windows ISO directly from Microsoft, which will require your product key to install. (Note: In many cases, this is included with your Windows computer.)
Step 2: Use Microsoft’s tool to create installation media for Windows.
Step 3: Look for the Sources folder, where you’ll find install.esd. This is the recovery partition, basically, but in its current state it is useless. To make it work for you, you have to first move it from the ISO or DVD to a location on your hard disk. Next, you need to convert it from install.esd to install.wim via some converters like WimConverter tool, and then copy the install.wim file to a new folder on your C:\ drive, labeled C:\Win81-Recovery. The next stage is to register the file so that Windows knows it is there and can create a recovery drive.
Step 4: Right-click the Windows Start screen button and select Command Prompt (Admin) on the desktop. Next, in the command line, enter:
REAGENTC /SetOSImage /Path C:\Win81-Recovery\INSTALL.WIM /Index 1
Tip: This will register the INSTALL.WIM file as your PC’s recovery image.





Step 5: Type: REAGENTC /Info.
Step 6: Type: exit.

source:
https://www.partitionwizard.com/part...partition.html

 

You already have a recovery partition. You can try:

reagentc /setreimage /path \\?\GLOBALROOT\device\harddisk0\partition3\Recovery\WindowsRE

You want to use setreimage, not setosimage to set up the recovery environment

You can make sure the recovery partition is partition 3 by running:

diskpart
select disk 0
list part
exit
exit

 

I tried the conversion, got the error "Disk layout validation failed".





The computer has only one disk with two system partitions, a SRP boot partition and the Windows partition. Also an extended partition with two data partitions.

 

@gdc88, were you able to convert to UEFI afterwards?

 

I got this error initially. When I looked in the logs (used /logs switch) it turned out it was complaining it did not have enough space to write the new EFI partition. I shrunk the C drive by a few Gigs (overkill) and then it worked.

 

I looked at the logs. Initially, the extended partition was not recognized (?). I converted the two data partitions to primaries, and then the four partitions were recognized, but the problem you mention appeared:

ValidateLayout: Too many MBR partitions found, no room to create EFI system partition.

I suppose this is the normal situation, the procedure should handle these cases automatically. Otherwise it becomes a cumbersome trial-and error process, which involves manual manipulation of the partitions. Not good.

 

Navy is on the right track. I didn't suggest that because I am not so familiar with reagent and couldn't walk you through it. But there's a whole slew of problems like this on eightforums, when people had used EASEUS to modify partitions and then couldn't access the recovery partition.

I would let Navy get your partitions in order with reagent.

 

I know it does not delete the old system reserve partition. I wonder what would hapoen if you deleted it first.

Anyway, I always delete recovery partitions as they are pretty useless in Windows 10 as you can use an installation drive to do the same thing anyway.

 

It sounds like this little utility is not quite up to prime time release. I would suggest that people try it once, and if it throws an error just use the manual method of converting if they still want to.

 

YES:

 

Some Tests Performed to understand how this works.

Test 1 - MBR has 4 primary Partitions









As expected, it failed to work. It is not clever enough to remove old SRP

Test 2 - MBR has 3 primary Partitions but no unallocated space









This validated fine - did not convert it.

Test 3 - MBR had 4 Primary Partitions but SRP was deleted first







This worked fine!





Note how it shrank OS rather than look for unallocated space.

Summary:

1) You cannot use mbr2gpt if 4 MBR partitions to start with - from log you can see it creates EFI first then does conversion to GPT.

(I do not see why it does not do conversion first then create EFI which would get round 4 MBR partition limit)

2) You can delete SRP first to reduce MBR partitions to 3.

Tutorial Recommendation

Add sentence saying if drive already had 4 primary partitions, you need to delete the System Reserved Partition first

Caveat: Not all MBR OS disks have an SRP for historical compatibility. Here it would be necessary to delete another primary partition eg a recovery partition


Note: I do not know how logical partitions would work. More tests needed.

 

I'd say if the tool fails, it may be best to clean install to UEFI instead.

 

Here's the problem, though....average Joe user deletes the System Reserved Partition and then the conversion to GPT and UEFI booting fails for another reason. Now what? Joe user is left with a computer that won't boot until one partition on that drive is made bootable again. My humble opinion is that it is dangerous for average Joe user to delete the System Reserved Partition their computer is booting from - at least without a major warning that deleting the partition will result in a failure to boot until either the conversion utility successfully creates an EFI System Partition or if it it fails another partition is made bootable.