We couldn’t update the system reserved partition

/01 — WHAT IT MEANS

What the message really means

You see it in one of two ways:

• Windows 11 Setup or the Installation Assistant stops with “This PC doesn’t currently meet Windows 11 system requirements. Here’s why: We couldn’t update the system reserved partition.”
• Windows Update downloads the yearly update, restarts, shows “Undoing changes made to your computer” and goes back to the desktop. Settings, Windows Update, Update history then lists it as Failed to install with an error code.

Despite the wording, your PC isn’t too old. On a modern PC the “system reserved partition” is the EFI system partition: a small hidden part of the drive, often only about 100 MB, that holds the files Windows needs to start. A version upgrade has to write new start-up files there and wants roughly 15 MB free. When it hasn’t got that, the upgrade either refuses to start or undoes itself after the restart.

Older PCs that were upgraded from Windows 10, and many laptops that came with a 100 MB partition from the factory, hit it most, and they hit it again at each yearly update.

The error codes you may see: 0x800F0922 in Update history, which Microsoft says means either the PC couldn’t reach Windows Update (a VPN can block it) or there isn’t enough free space in the System Reserved partition (Microsoft), and 0xC1900104 from Windows Setup. A yearly update that undoes itself can show a more general code too: on the Dell below it was 0x80242016. Whichever you have, the check in step 3 settles it in a minute.

/03 — CHECK IT FIRST

Check how full it is (changes nothing)

Right-click Start and choose Terminal (Admin) (on Windows 10, Windows PowerShell (Admin)), say Yes, then paste these lines one at a time, pressing Enter after each:

mountvol Y: /s
fsutil volume diskfree Y:
Get-ChildItem Y:\ -Recurse -Force -File | Sort-Object Length -Descending | Select-Object -First 12 FullName, Length

The first line gives the hidden partition the letter Y: for now (if Y: is already in use, use another spare letter such as S: in every line). The second shows its size and free space: under about 15 MB free is your problem. The third lists the biggest files on it, so you can see what’s filling it.

If mountvol gives an error instead, the PC may start the old (BIOS) way, where the partition is a visible “System Reserved” one instead; that’s a job for us rather than a paste.

/05 — WHAT NOT TO DO

The “fixes” to avoid

• The old del *.* instructions. Many websites repeat an old Microsoft recipe: type Y:, then cd EFI\Microsoft\Boot\Fonts, then del *.*. If the cd fails, or the window remembers a different folder on Y:, del *.* runs in the wrong place, and in the folder above the fonts that deletes the files your PC needs to start. It also skips hidden files, so it can free nothing while looking as though it worked. Use the full-path line above instead.
• Enlarging the partition with a partition tool. The top search results sell software that promises to make it bigger. To do it, the tool has to move your whole C: drive in a special start-up mode; if that is interrupted or goes wrong, the PC won’t start, and nothing remote can reach it. Only ever with a full backup image first, ideally on a workbench. We do this in our workshop when a partition is genuinely too small to ever be enough.
• A clean install to “get past it”. It wipes your programs and settings for a problem that 15 minutes of tidying fixes.

BitLocker: removing font files doesn’t need BitLocker turning off, but before any work on the start-up side of a PC it’s worth knowing where your recovery key is: see computer asking for a BitLocker recovery key.

/07 — THE QUICK WAY

Let our app check it, and tidy it

Version 36.4 of our free 365 PC Manager app checks this partition on its Windows Update page and says plainly when it’s too full for the next update. Its full service now tidies it safely, taking out the start-up fonts for languages the PC doesn’t use, and repairs damaged system files with Windows’ own tool. The Windows Update page itself only reads; the tidy happens when you run the full service.

FREE · WINDOWS 10 & 11 · NO SIGN-UP

Windows Update: is it really getting updates?

It reads Windows’ own update history — the same list as Settings, Windows Update, Update history — and says in plain words when the monthly update last installed, whether one update is failing over and over, and whether an update is waiting for a restart. It never installs, removes or changes anything.

In the app: My PC, then Windows Update.

Download 365 PC Manager free ↓What else it checks

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