Last Updated on August 30, 2026
If you are a regular Microsoft Windows user, then you are most likely used to there being Windows updates on a regular basis. You may have even installed Windows yourself once or twice (or many times) after building your own computer. For the most part, Windows updates and upgrades go smoothly.
But that does not mean you will avoid problems forever. You will eventually run into a serious roadblock that prevents you from performing these critical upgrades. This specific update failure brings your entire operating system migration to a grinding halt.
If you are trying to upgrade your computer and get a message that says, “We couldn’t update the system reserved partition”, you may think that you are out of luck and stuck with the current state of your PC. And if you are using the GPT (GUID Partition Table) scheme rather than MBR (Master Boot Record) scheme, you may find it difficult to fix this issue since you cannot extend the system partition when using the GPT scheme.
We will show you exactly how to free up space on a GPT configured EFI system partition. This manual command line process clears out unnecessary junk files safely. You can then finally upgrade your PC to the newest version of Windows.
Diagnosing the EFI Partition Problem
The image above is what you might see when you do not have enough free space on your EFI system partition to upgrade your computer. The message is incredibly vague. It completely fails to tell you what actually needs to be done to get past the block.
1. Check Windows Disk Management
If you open up the Windows Disk Management tool, you will see the exact size of your EFI system partition. You will notice that it is rather small and tends to be capped at around 100MB. This tiny storage limit fills up quickly with redundant boot files over the years.
2. Verify the GPT Partition Style
You will also notice that there is no graphical way to expand the size of the EFI system partition from Disk Management. This restriction exists mainly because it uses the strict GPT partitioning scheme. Right-click the disk itself, choose Properties, and go to the Volumes tab to confirm you are using GPT for your partition style.
3. Understand Third-Party Tool Limitations
Standard partitioning software cannot bypass this core architectural restriction. Even if you use a powerful third-party disk partition editor such as NIUBI Partition Editor, you will fail to expand the EFI system partition. The operating system actively protects this specific boot sector from being resized while Windows is running.
Free Up Space on the EFI System Partition
To get around this hard limitation, you must manually free up space on the GPT configured EFI system partition. This clearing process allows the Windows installer to write its new boot files successfully. You will need to open an administrative command prompt to execute these specific commands.
1. Launch the Command Prompt as Admin
Click your Windows Start button and type cmd into the search bar. Right-click the Command Prompt application and select Run as Administrator. You must have elevated privileges to mount hidden system drives.
2. Mount the EFI System Partition
You need to force Windows to assign a drive letter to the hidden boot sector. Type mountvol y: /s into the terminal and press Enter. This specific command mounts the EFI system partition directly to the Y drive so you can access the files.
3. Access the New Drive Letter
Now you must switch your active terminal session over to this newly mounted partition. Type y: and press Enter to change your directory focus. Your command prompt cursor will now reflect the Y drive path.
4. Navigate to the Boot Fonts Directory
The bulk of the wasted space inside this partition comes from unnecessary international language font files. Type cd EFI\Microsoft\Boot\Fonts into the prompt and press Enter. This changes your active path directly to the hidden Fonts directory.
5. View the Directory Contents
You should verify you are in the correct location before deleting anything. Type dir and press Enter to view the contents of the Fonts directory. Make sure you see the .ttf font files listed on your screen so you know you are targeting the right folder.
6. Delete the Redundant Font Files
Now you can safely delete all of these font files to clear out the required storage space. Type del . ** into the terminal and press Enter to execute the deletion. Confirm the prompt by pressing Y if the system asks you to verify the bulk removal.
7. Unmount the EFI Partition
Once the deletion process is complete, you will have successfully increased the amount of free space on your EFI system partition. You must unmount the drive to protect it from further accidental changes. Type mountvol y: /d and press Enter to hide the partition again.
8. Retry the Windows Upgrade
Now you can try to upgrade or update your computer again using the official Windows installation assistant. The installer will easily find enough space on your GPT configured EFI system partition to write the new bootloader. After you perform your upgrade successfully, the system will automatically re-add the necessary fonts to the folder.
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