Windows 10: Unable to boot after mbr2gpt conversion, recovery drive missing

HelloContext in case it mattersI’m working on an older Samsung computer that I’ve been updating for my mom. I was able to upgrade from Windows 7 to Windows 10. I then upgraded the ram and installed a 250gb SSD. There was an issue with the graphics card Intel hd graphics 3000 but it worked fine as long as I used the basic microsoft driver. I created a restore point. So far so good.I tried to create a backup to the old HD but kept getting the message that there was insufficient space. I deleted some fonts from the System partition, so 43mb free space. Still failed. I then tried to convert th

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Can't boot after running mbr2gpt

Hello all. I was recently working on upgrading one of my workstations from Window 10 to Windows 11. The first step should have been making a backup, but of course I skipped that. I ran mbr2gpt /validate - Validation completed successfully Then I ran mbr2gpt /validate /allowFullOS - Validation completed successfully Finally I ran mbr2gpt /convert and here is what it kicked out: MBR2GPT: Attempting to validate disk 0 MBR2GPT: Retrieving layout of diskMBR2GPT: MBR2GPT: Validating layout, disk sector size is: 512 bytes MBR2GPT: Trying to shrink the OS partition MBR2GPT: Creating the EFI system partition MBR2GPT: Installing the new boot files MBR2GPT: Performing the layout conversion MBR2GPT: Migrating default boot entry MBR2GPT: Adding recovery boot entry MBR2GPT: Fixing drive letter mapping MBR2GPT: Conversion completed successfully Call WinReReapir to repair WinRE MBR2GPT: Failed to update ReAgent.xml, please try to manually disable and enable WinRE. MBR2GPT: Before the new system can boot properly you need to switch the firmware to boot to UEFI mode! I then went into the bios and changed to UEFI and enabled Secure Boot but Windows was unable to boot. I attepted startup repair - no luck. I then tried to start with a Windows 10 install disk. When I did this, I was unable to see the drives. I then changed back from UEFI to Legacy and started up with the Windows 10 install disk. Now I could see the disks. I ran chkdsk /r and then rebooted Instead of Windows loading, I'm getting a softthings technologies display that shows when the drive was erased (from before we purchased it). Strange. Just as an FYI - it shows this data if it is helpful Dell Precision 5820 Tower NVMe PC601 NVMe SK hynix 512 GB - 476.94 GB - NVME ( - MBR) NVMe Micron 2200S NvMe 1024GB - 953.87 GB - NVME( - MBR) [] - 0.00 GB - Unknown (C - MBR) As I'm writing this, I'm running clonezilla to backup the data from the drive. This thread appears to be identical to my issue: Need Help with MBR2GPT But the issue is, if I'm stil in UEFI, I can run reagentc /info BUT I can't run the following: reagentc /disable reagentc /enable I've still got about 30 minutes left before my backups are done but would love to get your feedback. Thanks in advance!

 

How can I migrate a Windows 10 from BIOS/MBR boot to UEFI/GPT without reinstalling?

In Windows 10 v1703 (Creators Update, Build 15063), there is a tool called MBR2GPT.EXE included which does all steps.

Best is to boot from a Win10 v1703 DVD/USB drive to the repair option (WinPE) and run Command prompt (cmd.exe) under repair options. Now use diskpart and list command to see all drives.

Now look or the disk number where your Windows is installed. This number is important for next step. Now run mbr2gpt /convert /disk:ID with the ID:

Now, reboot the PC, enter the UEFI and change the mode from BIOS/legacy to UEFI only:





Now save the changes, reboot and Windows 10 should boot. When you run msinfo32.exe you should see that Windows 10 runs now in UEFI mode.

 

Missing Recovery partions - is that a problem?

In preparation for converting my boot drive from MBR to GPT I ran Disk Management and noticed I have no Recovery partition. This has caused no problem or I would have noticed it before, but is it going to be problematic in the future? MBR2GPT /validate reported no problem so I assume the conversion will work but I would rather fix things that need fixing before doing the conversion.

BTW, my test PC had two recovery partitions (which did cause MBR2GPT to choke) so this all averages out, I guess.