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0x80070643 installing KB5034441 — WinRE partition too small

The WinRE servicing update needs about 250 MB free in the recovery partition. Most Windows 10 machines were imaged with a 500 MB partition that has nowhere near that free, so the update fails and retries forever.

What you see

Windows Update repeatedly offers KB5034441 and fails with 0x80070643 — ERROR_INSTALL_FAILURE. The error text mentions a fatal error during installation, which is misleading; nothing is actually broken.

What is actually wrong

Not a corruption problem at all — it is a disk space problem inside the recovery partition, which is normally hidden and has no free space to grow into because the OS partition sits immediately before it.

Codes and articles

0x8007064380070643KB5034441KB5034440KB5028997

Fixes (2)

Shrink the OS partition and grow the recovery partition
Elevated command prompt in Windows20–30 minuteshigh risknot reversible

You want the update installed. This repartitions the disk — take a backup first, and do not run it on a machine without one.

  1. Take a full backup or a disk image. This step is not optional; the rest of this procedure deletes a partition.

    diskpart delete override removes the recovery partition outright. If step 6 fails you need a way back.

  2. Disable WinRE and note the location it reports.

    Command Prompt
    reagentc /disablereagentc /info

  3. Start diskpart and select the disk and the Windows partition.

    Command Prompt
    diskpartlist disksel disk 0list part

  4. Shrink the Windows partition by 250 MB. Substitute the partition number you saw for the large NTFS one.

    Command Prompt
    sel part 3shrink desired=250 minimum=250

  5. Delete the old recovery partition. On a GPT disk it is the one with id de94bba4-06d1-4d40-a16a-bfd50179d6ac.

    Command Prompt
    sel part 4delete partition override

  6. Create the replacement. GPT disks use the first block, MBR disks the second.

    Command Prompt
    create partition primary id=de94bba4-06d1-4d40-a16a-bfd50179d6acgpt attributes=0x8000000000000001format quick fs=ntfs label="Windows RE tools"exit

  7. Re-enable WinRE and confirm it registered.

    Command Prompt
    reagentc /enablereagentc /info

  8. Run Windows Update again.

Confirm it workedreagentc /info reports Windows RE status: Enabled with a valid location, and the update installs.
Command Prompt
reagentc /info
If you need to undo itThere is no in-place rollback once the partition is deleted — restore from the image taken in step 1.
Stop the update being offered
Windows5 minuteslow riskreversible

The machine is otherwise healthy and you would rather not repartition. WinRE still works; it just does not get this particular hardening fix.

  1. Confirm WinRE is actually present and enabled — if it is, the only thing you lose by skipping the update is the patch itself.

    Command Prompt
    reagentc /info

  2. Download the Show or hide updates troubleshooter (wushowhide.diagcab) from Microsoft.

  3. Run it, choose Hide updates, tick KB5034441 and finish.

Confirm it workedWindows Update no longer lists the update and stops reporting the failure.
If you need to undo itRun the same troubleshooter and choose Show hidden updates.

Reference

KB5034441 — Microsoft Support ↗KB5028997 — resize the recovery partition ↗

Related faults

A machine is broken by the latest update and needs it removedWindows"Automatic Repair couldn't repair your PC" — the repair loopWindows"There was a problem resetting your PC" — Reset this PC failsWindows0x800f0922 — update fails, System Reserved partition full or no route to MicrosoftWindows

Where this stops. This write-up was written and checked by hand. It says what each step changes, how to confirm it worked and how to reverse it, and anything destructive is flagged before you reach it. If it does not match what your machine is doing, search the Support Centre for the exact code or message — and when something needs a person, get in touch.