I was called for help yesterday by a friend who had a problem with his laptop, an older but still fully functional Acer laptop. His computer was indeed infected by a malicious adware that displayed pop-ups in his Google Chrome browser after visiting streaming sites. After disinfecting his computer with ZHPCleaner and reinitializing Google Chrome, his web browser was working properly again. On the other hand, I noticed that his Windows 10 operating system was no longer updated, which is never good from a cybersecurity point of view… Unable to install the 1903 version of Windows 10, Windows Update systematically interrupted the installation of the update by indicating the error message lros of the attempt to update Windows: ” This PC can not run Windows 10. Unable to update the reserved partition of the system” .
This error message is sometimes accompanied in Windows log files by the error code 0xc1900104 or the error code 0x800f0922.
What does the “Unable to update reserved system partition” message mean?
The reserved system partition is a hidden partition of the hard disk which stores Windows boot information among other things. Some third-party applications such as antivirus software can also use this partition.
During the installation of a Windows update, this partition is checked by the installer of the update which verifies, among other things, that there is enough space available on the hard disk. The message “Unable to update the reserved partition of the system” is most often caused by a lack of space on this partition, which causes the error in installing the Windows 10 update(Windows 1909 or Windows 1903 update).
Solution for Windows 10 installation problem “Unable to update the reserved partition of the system”?
Methods that failed
I tried several tricks to try to fix the Windows 10 installation error problem:
- Scanning the hard drive with free antivirus software and removing adware (with ZHPCleaner, AdwCleaner disinfection software)
- Hard drive scanning with chkdsk and repair of hard drive errors
- Windows 10 disk image repair with the DISM command: DISM /Online /Cleanup-Image /RestoreHealth
- Cleaning the hard disk with the Windows 10 utility
Unfortunately, none of these techniques worked and I was still stuck with the same installation error.
Free up space on the reserved system partition to solve the “Cannot update reserved system partition” error in Windows 10
I found the solution on the web via a Microsoft help page (https://support.microsoft.com/fr-fr/help/3086249/we-couldn-t-update-system-reserved-partition-error-installing-windows) explaining how to gain storage space on the system partition. This allows to proceed to the installation of the Windows 10 1903 update.
Problem: the help provided by Microsoft is a (very bad) translation of an English article (https://support.microsoft.com/en-us/help/3086249/we-couldn-t-update-system-reserved-partition-error-installing-windows) with errors in the commands to enter … So here is the detailed procedure corrected in French!
The different steps to follow to solve the installation problem of the Windows 10 1903 update (for informed users who are already used to using the Windows 10 command prompt)
Know the partition type of the system partition
- Right click on the Windows Start menu and click on Disk Management (or use the Windows keyboard shortcut Windows key + R, type diskmgmt.msc and press OK)
- Find the disk where the partition reserved for the system is installed, right click on the disk (on the far left) and click on Properties.
- Click at the top of the menu on the Volumes tab of the Hard Disk Properties window and find the Partition Type line.
The rest of the tutorial will depend on the type of partition: MBR partition(Partition type: Main boot sector) or GPT partition(Partition type: GUID partition table (GPT)).
Solve the “Cannot update reserved system partition” problem for a GPT partition
This is the simplest case. Not the one of my friend, of course… For all the steps of this tutorial, you have to type the command in the command prompt and then press the Enter key on your keyboard to validate the entered command. To avoid mistakes and save time, I invite you to copy and paste the commands from this article.
- Open the Windows 10 command prompt (admin) by right-clicking on the Windows 10 Start menu (bottom left of your screen) and selecting Command prompt (admin) . If you can’t find it, I recommend reading my article on Windows 10 command prompt not found.
- Type in the command prompt: mountvol Y: /s This will assign a letter to your system partition to free up space on the partition.
- Type in the command prompt: Y: to position you in the system partition then cd EFIMicrosoftBootFonts then the Enter key of your keyboard to validate the command to position you in this folder of the partition reserved for the system.
- Once in the folder, type: del *.* to delete all the font files stored in this folder. This will normally save you enough space to proceed with the installation of Windows 10 updates.
Solve the “Cannot update reserved system partition” problem for an MBR partition
Unfortunately, the procedure is a bit longer, with more commands to enter, for an MBR partition… Here again, copy and paste the commands below, it’s faster and safer because there is less risk of typing errors.
Here’s how to free up space on the Windows 10 system partition for an MBR partition:
- Open the Disk Management utility as described above, then right-click on the system partition and select Change drive letter and paths
- Click on the Add button and then assign the drive letter Y using the drop-down list and click on OK.
- Open the Windows 10 Command Prompt (admin) by right-clicking on the Windows 10 Start menu (bottom left of your screen) and selecting Command Prompt (admin).
- Type in the command prompt: Y: (then Enter to validate the command) to position you in the system partition then cd BootFonts (then press Enter to validate the command).
- Type in the command prompt: takeown /f . /r /d O
- Type in the prompt: icacls Y:* /save %systemdrive%NTFSp.txt /c /t
- Type whoami in the command prompt, then note the username given (usually the name of your PC and your username) and type the following command:
icacls . /grant to_replace_by_the_name_requested_by whoami_just_before:F /t (make sure to type your username just before and do not put any space between this name and :F)
Ex: icacls . /grant steve-pcutiliser:F /t
- Delete all the font files by typing del *.* and pressing the Enter key. You have just freed up space on the system partition.
- Now you just need to restore the permissions! Start by typing: icacls Y:/restore %systemdrive%NTFSp.txt /c /t
- Enter : icacls . /grant system:f /t then icacls Y: /setowner “SYSTEM” /t /c
- Go back to the disk manager and delete the drive letter of the system partition by right-clicking on the partition reserved for the system and then Modify the drive letter and access paths and then click on the Delete button.
Once this manipulation was done, I had the good surprise to see that space had been freed on the partition reserved for the system and I could finally install Windows 10 version 1903 successfully!