Windows update: System partition full or not enough space

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Introduction

When running Windows Update, you may encounter errors such as:

“System reserved partition is full”
or
“There is not enough space to install updates.”

This typically happens when the System Reserved Partition (SRP) or the EFI partition does not have enough free space to handle new update files. Many older systems ship with only 100 MB for this partition, while newer Windows updates may require 500 MB or more.

In this article, you’ll learn:

• Why the system partition fills up
• How to check the partition size
• The exact commands to fix the issue
• Best practices to prevent it in the future

Why This Happens

The System Reserved Partition contains:

• Boot configuration data
• Recovery files
• BitLocker encryption files (if enabled)
• Temporary storage required during major Windows updates

If the partition runs out of space, Windows Update fails with errors like 0x800F0922.

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Step-by-Step: Fix the Problem

Step 1: Open Command Prompt as Administrator

Search for cmd in the Start menu, right-click, and select Run as administrator.

Step 2: Check the Disk Layout

Run the following commands to view partitions:

diskpart
list disk
select disk 0
list partition

diskpart
list disk
select disk 0
list partition

You will see the System Reserved or EFI partition (usually between 100 MB and 500 MB).

Step 3: Free Space or Extend the Partition

3.1 Free up space on GPT Partition

Execute CMD or PowerShell as an administrator then mount the system partition.

mountvol y: /s
y:
cd EFI/Microsoft/Boot/Fonts
del *.*

mountvol y: /s
y:
cd EFI/Microsoft/Boot/Fonts
del *.*

cd EFI/HP/BiosUpdate
del *.*

cd EFI/HP/BiosUpdate
del *.*

cd EFI/HP/DEVFW
del *.*

cd EFI/HP/DEVFW
del *.*

Then confirm by typing Y and press enter. Now restart the update.

3.2 Add space on GPT Partition

diskpart
select disk 0
list partition # looks up all partitions
select partition 1 # if this is the system partition
extend size=200 # extents the partition with 200mb

diskpart
select disk 0
list partition # looks up all partitions
select partition 1 # if this is the system partition
extend size=200 # extents the partition with 200mb

Best Practices

• Create the System Reserved Partition with at least 500 MB on new installations.
• Regularly clean temporary files with cleanmgr.exe or Storage Sense.
• Ensure you have a backup before modifying partitions.
• If BitLocker is enabled, back up your recovery key before making changes.

Conclusion

The “System partition full” error during Windows Update happens when the System Reserved/EFI partition lacks enough free space. By checking the partition size and applying the commands to extend or free space, updates can install successfully again.

Source: Microsoft Learn Q&A
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