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How to fix Windows Update Error 0x80070643

Error code: WU-0x80070643

What this error means

An update fails with 0x80070643, which is the Windows Update form of installer error 1603, ERROR_INSTALL_FAILURE: an installation failed. The code is generic, so the update's name matters. A well-known case is the Windows Recovery Environment (WinRE) update for Windows 10, originally KB5034441: Microsoft says it needs 250 MB of free space in the recovery partition and is not needed if WinRE is not enabled. Other cases, such as Microsoft Defender or .NET updates, are usually fixed by resetting Windows Update and installing the update again.

Updated

Applies to
Windows 11 and Windows 10
Difficulty
Beginner to advanced (partition step)
Before changes
Low; resizing partitions in step 3 can cause data loss if done wrong

Reviewed by Matyáš Rada · Documentation checked: 2026-10-31 · Checked against Microsoft's WinRE update and partition resizing articles; not tested on every configuration.

Before you begin

Open Settings > Windows Update > Update history and note the name and KB number of the update that fails. The steps depend on which update it is. If Windows cannot start, see the startup guide.

Work through these checks

0 of 7 complete
01Check which update fails

0x80070643 is a general installation failure, so the fix depends on the update.

  1. A "Windows Recovery Environment update" (for example KB5034441, later replaced by KB5042320) on Windows 10: go to step 2.
  2. A Microsoft Defender, .NET or other update: go to step 4.
What to expect

You know which part of the guide applies.

If it does not help

If several updates fail, start with step 4.

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02For a WinRE update, check whether WinRE is enabled

Microsoft says the WinRE update is only needed when the recovery environment is enabled.

  1. Open Command Prompt as administrator and run reagentc /info.
  2. If Windows RE status is Enabled, the update applies and needs space (step 3). If it is Disabled, Microsoft says the update is not needed.
What to expect

You know whether the update is required.

If it does not help

Microsoft retired KB5034441 and moved its content to KB5042320, which is not offered to PCs that do not need it.

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03Make room in the recovery partition (advanced)

Microsoft says the WinRE update requires 250 MB of free space in the recovery partition, and devices without it need to increase the partition manually.

  1. Back up your files first.
  2. Follow Microsoft's article KB5028997, "Instructions to manually resize your partition to install the WinRE update", step by step (it uses reagentc and diskpart).
  3. Then run Windows Update again.

Partition changes can cause data loss if a wrong disk or partition is selected. Follow Microsoft's instructions exactly.

What to expect

The WinRE update installs.

If it does not help

If you are not comfortable with diskpart, the update can be left uninstalled; it only affects the recovery environment.

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04Restart and clear the update cache

A damaged download often makes an update installation fail.

  1. Restart the PC with Restart and try the update again.
  2. If it fails, open Command Prompt as administrator and run net stop wuauserv and net stop bits, then ren %systemroot%\SoftwareDistribution\Download Download.bak, then net start bits and net start wuauserv.
  3. Check for updates again.

Use Command Prompt, not PowerShell, for the ren command.

What to expect

The update downloads again and installs.

If it does not help

If it still fails, repair system files in step 5.

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05Repair system files

Damaged system files can make installations fail.

  1. In Terminal (Admin), run DISM /Online /Cleanup-Image /RestoreHealth and then sfc /scannow.
  2. Restart and try the update.
What to expect

The update installs.

If it does not help

If it fails, install it manually in step 6.

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06Install the update manually

A manual installation shows clearer errors and avoids the automatic update process.

  1. For Windows updates, download the KB number from the Microsoft Update Catalog (catalog.update.microsoft.com) and run the .msu file.
  2. For Microsoft Defender, open Windows Security > Virus & threat protection > Protection updates > Check for updates.

Download updates only from Microsoft.

What to expect

The update installs.

If it does not help

If a manual installation reports error 1603, see the error 1603 guide on this site.

Browse related errors
07Repair the product being updated

If the update is for an installed program (such as .NET or Office), a damaged installation of that product can make every update fail.

  1. In Settings > Apps > Installed apps, find the product, choose Modify or Repair if available.
  2. Or reinstall the latest version of the product from Microsoft, then run Windows Update again.
What to expect

The product's updates install normally.

If it does not help

If many different updates fail, an in-place upgrade (setup.exe from the Windows ISO, keeping files and apps) repairs Windows itself.

Browse related errors

Possible causes

  • Too little free space in the WinRE recovery partition (Windows Recovery Environment updates)
  • A damaged Windows Update cache
  • A problem with the Windows Installer or the installed product being updated
  • Damaged system files
  • Security software interfering with the installation

Sources & further reading