Windows 10: MBR2GPT : Windows Now Has Both EFI and C: Acting As System Partition

Following running MBR2GPT to convert from legacy to UEFI boot, I got the error "REAGENTC.EXE: Unable to update Boot Configuration Data." Following further investigation I found that Windows seems to have retained the legacy bootloader and added the UEFI bootloader. As such, both the EFI System Partition and C: Partition are attempting to act as the system partition see screenshot. This is preventing me from enabling REAGENTC. What can be done?

:)

 

Cannot find room for the EFI system partition.

Hi Artti,



Welcome to Microsoft Community.

Some community members speculate that such phenomena may be related to the physical structure of the disk/partition.

• Issues using MBR2GPT for Windows 11 Upgrade - Microsoft Community
  

Some community members speculated that the disk may need to be revalidated.

• Cannot find room for the EFI system partition Error - Microsoft Community
  

Some community members speculated that the EFI partition may need to be configured manually.

• mbr2gpt fails with "Cannot find room for the EFI system partition." - Microsoft Community
  

The Answer community is primarily involved in general guidance at the usage level for products.

I wish I could handle your problem, however, analyzing issues related to MBR2GPT requires deeper knowledge of the underlying workings of the MBR2GPT tool, which is beyond our technical reserves.

The content in the following links described basic information related to the MBR2GPT tool.

Change a Master Boot Record (MBR) into a GUID partition table (GPT) disk | Microsoft Learn

MBR2GPT - Windows Deployment | Microsoft Learn

The issue on MBR2GPT is out of reach of the response support community.

For further professional assistance, it is more suitable for publishing on Microsoft Learn (English only), you can click on "Ask a question", there are experts who can provide more professional insights in that place

Here is a link to the forum where you can raise specific scenarios and share your idea to help analyze the problem.

• Windows 10 - Microsoft Q&A
  

Sincerely hope that your question will be dealt with appropriately after contact the correct department.



Thanks for your patience and cooperation.

Best Regards,

| Microsoft Community Technical Support

 

Cannot find room for the EFI system partition when trying to do mbr2gpt

There is a method you may try. Get rid of the System Reserved Partition or the Recovery Partition or both. MBR2GPT may decide to create the EFI System Partition on 549 MB of unallocated space if available. Run

bcdboot C:\Windows /s C:

as an administrator to add startup files to drive C, then mark drive C as active. Do not mark drive C as active without running the bcdboot command.

Reboot and delete System Reserved.

 

MBR2GPT fails with error - Cannot find room for the EFI system partition.

Regarding this image, which partition should I extend?

The problem wasn't that I didn't have enough space to update, it was the MBR2GPT error: "cannot find room for the EFI system partition"