Windows Update error 0x80070643: how to fix it

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0x80070643 is a generic "fatal error during installation" code, so the right fix depends on which update failed. If it is KB5034441, the recovery partition needs to be resized. For other updates, repairing system files and resetting the Windows Update components is the usual route.

Applies to:Windows 1021H2, 22H2Windows 11
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What it means

0x80070643 is a generic installation failure code, "fatal error during installation". It does not name a cause. It only says that an update installer gave up, so two people with the same code can have different problems.

The best-known case is KB5034441, a Windows Recovery Environment (WinRE) update from January 2024 aimed at Windows 10. It fails when the recovery partition has too little free space. Other updates can fail with the same code too, for example Defender definition updates (KB2267602) and .NET Framework updates. So first find out which update is failing, then pick the matching fix below.

Microsoft's KB5028997 page covers the partition resize but does not mention 0x80070643 by name. The link between the two comes from community and news reports about KB5034441.

Symptoms and causes

You are likely dealing with this problem if:

  • Windows Update shows "There were some problems installing updates" with (0x80070643), and a retry fails again.
  • Update history lists KB5034441 as the failed update (recovery partition case).
  • Event Viewer has System event ID 4502, "Windows Recovery Environment servicing failed", with ErrorPhase 2 (recovery partition case).
  • The failed update is KB2267602 (Defender definitions case).

The usual causes, most common first:

Recovery partition too small (KB5034441 and other WinRE updates)
The WinRE update needs free space in the recovery partition. If the partition is too tight, servicing fails and Windows Update reports the generic code. Microsoft's fix is to enlarge the partition by 250 MB.
Corrupted Defender definition store (KB2267602)
If the failing update is a Microsoft Defender definition update, the Defender component itself may be damaged. This comes from a third-party troubleshooting guide.
Damaged Windows Update components, system files or .NET Framework
A broken update cache, corrupted system files or a damaged .NET Framework can make an installer fail with this generic code.
Third-party antivirus interference
Some security software can block an installer mid-way. This is reported by a third-party guide, not by Microsoft.

How to fix it

Work through these in order. They start with the quickest, safest checks and move to deeper repairs; stop as soon as the problem is gone.

1.Find out which update is failing and retry

Easy

The code is generic, so the KB number decides which of the later fixes applies. A plain restart and retry also clears some one-off failures.

  1. Open Settings > Windows Update > Update history and note the KB number next to the failed update.
  2. Restart the PC, return to Windows Update and click Retry.
  3. If the failed update is KB5034441, go to the recovery partition fixes. If it is KB2267602 or something else, continue with the next fixes.

2.Run the troubleshooter, repair system files and update .NET

Easy

These built-in repairs cover damaged system files and .NET, which are common causes for non-WinRE failures.

  1. Open Settings > System > Troubleshoot > Other troubleshooters and run the Windows Update troubleshooter.
  2. Open Command Prompt as administrator and scan system files, then restart.
    Command Promptrun as administrator
    sfc /scannow
  3. Install the latest .NET Framework from Microsoft's download page. Do not uninstall the versions you already have.
  4. Retry the update.

3.Repair or reset Windows Security (Defender failures)

EasyChanges settings

If the failing update is the Defender definition update (KB2267602), repairing the Windows Security app can fix the damaged component.

Before you start: Resetting Windows Security may reset some of its settings. Note any custom settings first.

  1. Open Settings > System > System components, find Windows Security and open Advanced options.
  2. Click Repair. If the update still fails, click Reset.
  3. Run Windows Update again.

4.Test with third-party antivirus switched off

EasyChanges settings

If you use a non-Microsoft antivirus, it may be blocking the installer. This only tests that theory.

Before you start: Turn the antivirus back on right after the test, whether or not the update succeeds. Stay offline from risky sites meanwhile.

  1. Temporarily turn off the third-party antivirus from its own settings.
  2. Install the update from Windows Update.
  3. Turn the antivirus back on immediately.

5.Install the update manually from the Microsoft Update Catalog

Easy

A manual install bypasses the Windows Update download and cache, which sometimes gets past the error.

  1. Search for the failed KB number in the Microsoft Update Catalog and download the package that matches your Windows version and system type.
  2. Run the downloaded file and restart when asked.

6.Reset the Windows Update components

ModerateChanges settings

Renaming the two cache folders forces Windows to rebuild them, which is a standard step when update installs keep failing.

Before you start: Create a restore point first. The old folders are kept under the new names, so you can undo the rename if needed.

  1. Open Command Prompt as administrator and run these commands in order.
    Command Promptrun as administrator
    net stop wuauserv
net stop cryptSvc
net stop bits
net stop msiserver
ren C:\Windows\SoftwareDistribution SoftwareDistribution.old
ren C:\Windows\System32\catroot2 catroot2.old
net start wuauserv
net start cryptSvc
net start bits
net start msiserver
  2. Restart the PC and run Windows Update again.

7.KB5034441: confirm the recovery environment is the cause

Moderate

Before touching partitions, check that WinRE is really involved.

  1. Open Command Prompt as administrator and view the WinRE status and location.
    Command Promptrun as administrator
    reagentc /info
  2. Open Event Viewer > Windows Logs > System and look for event ID 4502 (WinRE servicing failed).
  3. If there is no event 4502 and the failed update is not KB5034441, the recovery partition is probably not your problem. Go back to the general fixes above instead of resizing anything.

8.KB5034441: resize the recovery partition manually

AdvancedBack up first

This is Microsoft's KB5028997 procedure. It gives the recovery partition room for the WinRE update.

Before you start: Back up your important files first, and ideally make a full system image. Microsoft's page includes no backup instructions. The steps only work if the recovery partition sits directly after the OS partition on the same disk. Check the disk and partition numbers carefully before running delete partition override, because deleting the wrong partition can make Windows unbootable.

  1. If the drive is protected by BitLocker or device encryption, save your recovery key and suspend protection before changing partitions. Resume it when you are done.
  2. Open Command Prompt as administrator. Note the WinRE disk and partition, then turn WinRE off.
    Command Promptrun as administrator
    reagentc /info
reagentc /disable
  3. Start DiskPart and list the disks. A disk with an asterisk in the Gpt column is GPT. A disk without one is MBR. Write this down, because you need it later.
    Command Promptrun as administrator
    diskpart
list disk
  4. Select the OS disk and list its partitions. Confirm that the disk is the same one reagentc /info reported for WinRE, and that the recovery partition comes immediately after the OS partition. If it does not, or the disk numbers differ, stop here: this procedure does not apply to your layout.
    Command Promptrun as administrator
    sel disk <OS disk number>
list part
  5. Shrink the OS partition by 250 MB. If shrink fails because Windows cannot free 250 MB, stop, type exit, run reagentc /enable to restore WinRE, and get help instead of continuing.
    Command Promptrun as administrator
    sel part <OS partition number>
shrink desired=250 minimum=250
  6. Select the old recovery partition and delete it. Double-check the partition number first.
    Command Promptrun as administrator
    sel part <WinRE partition number>
delete partition override
  7. If the disk is GPT, create the new recovery partition with these commands.
    Command Promptrun as administrator
    create partition primary id=de94bba4-06d1-4d40-a16a-bfd50179d6ac
gpt attributes =0x8000000000000001
  8. If the disk is MBR, create it with this command instead.
    Command Promptrun as administrator
    create partition primary id=27
  9. Format the new partition. On MBR disks, also run set id=27. Then list volumes and exit DiskPart.
    Command Promptrun as administrator
    format quick fs=ntfs label="Windows RE tools"
list vol
exit
  10. Turn WinRE back on and verify its status.
    Command Promptrun as administrator
    reagentc /enable
reagentc /info
  11. If creating the partition fails, run reagentc /enable to restore the previous WinRE state, then stop and get help rather than retrying blindly.
  12. Run Windows Update again and retry KB5034441.

Check that it worked

  • The update shows as successfully installed in Settings > Windows Update > Update history, and Windows Update no longer reports 0x80070643.
  • For the recovery partition fix, reagentc /info shows Windows RE status as Enabled and points to the new partition.

If it still fails

  • If the recovery partition is not located directly after the OS partition, the manual procedure does not apply. Ask the PC maker or Microsoft support before changing partitions.
  • Note the exact KB number and the event 4502 details from Event Viewer, then contact Microsoft Support or your PC manufacturer.

Questions

Is 0x80070643 only about KB5034441?

No. It is a generic installation failure code. KB5034441 is the best-known cause, but Defender definition updates, .NET Framework updates and other updates have also failed with it.

Sources

  1. KB5028997: Instructions to manually resize your partition to install the WinRE updateOfficial · Microsoft Support
  2. Fix Windows Update Error 0x80070643 · Prajwal Desai

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