How to Fix Install Error 0x80070643 in Windows

Error 0x80070643 is Windows' code for ERROR_INSTALL_FAILURE: something tried to install and didn't finish. Years ago it often appeared when people installed Microsoft Security Essentials. Today it also shows up in Windows Update, next to an update that keeps failing. Start with section 1 if you were installing Security Essentials; otherwise work through sections 2 to 7 in order and check for updates again after each one.

1. Installing Microsoft Security Essentials? You Don't Need It

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Microsoft Security Essentials was Microsoft's free antivirus from the Windows 7 era. Windows 7 support ended on January 14, 2020, and Microsoft stopped updating the Security Essentials program itself after that date. Installing it on a modern PC isn't the fix.

Windows 11 and Windows 10 already include the Windows Security app, with Microsoft Defender Antivirus built in. To check that you're protected:

1. Search for Windows Security in the Start menu and open it.
2. Select Virus & threat protection.
3. Select Quick scan to run a check now.

If you're still on Windows 7, that PC no longer gets security updates from Microsoft, and Microsoft recommends moving to a newer version of Windows.

Expected result: Windows Security opens and the quick scan finishes, so there's nothing left to install.

2. Restart and Try the Update Again

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Start with the simplest checks from Microsoft's update troubleshooting guide: power, connection and a fresh check for updates.

1. Select Start > Power > Restart.
2. Make sure your PC is plugged in and connected to the internet.
3. Select Start > Settings > Windows Update > Check for updates.

On Windows 10: the path is Settings > Update & Security > Windows Update > Check for updates.

Expected result: the update installs, or fails again with the same code (move on to section 3).

3. Run the Windows Update Troubleshooter

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Microsoft's Windows Update troubleshooter runs diagnostics and tries to fix the problem for you. Microsoft suggests running it first in the Get Help app.

1. Open the Get Help app and run the Windows Update troubleshooter there.
2. If that doesn't solve it, select Start > Settings > System > Troubleshoot > Other troubleshooters, and select Run next to Windows Update.
3. When it finishes, restart and check for updates again.

On Windows 10: use Settings > Update & Security > Troubleshoot > Additional troubleshooters > Windows Update > Run the troubleshooter.

Expected result: the troubleshooter reports what it fixed, and the update installs on the next check.

4. Free Up Drive Space

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Updates need room to download and unpack. Microsoft's troubleshooting guide asks for at least 16 GB of free space on 32-bit Windows and at least 20 GB on 64-bit Windows.

1. Select Start > Settings > System > Storage > Cleanup recommendations.
2. Review the categories, select the items you don't need, and select Clean up.

On Windows 10: search for Disk Cleanup, choose your drive, tick the file types to delete, and select Clean up system files for more space.

Expected result: your system drive has more free space, and the update has room to install.

5. Repair Windows System Files With DISM and SFC

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Damaged system files can stop updates from installing. Microsoft recommends running DISM first and System File Checker second.

1. Type cmd in the search box, right-click Command Prompt and select Run as administrator.
2. Type DISM.exe /Online /Cleanup-image /Restorehealth and press Enter. Wait for it to finish.
3. Type sfc /scannow and press Enter. Don't close the window until verification reaches 100%.
4. Restart, then check for updates again.

Expected result: SFC reports that it found no integrity violations, or that it found corrupt files and repaired them. See How to Repair System Files Using System File Checker for more detail.

6. Clear the Windows Update Cache

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Corrupt files in the update download folder can make the same update fail again and again. Clearing the folder makes Windows download fresh copies.

1. Press Windows key + R, type services.msc and press Enter.
2. Right-click Windows Update and select Stop.
3. Open File Explorer, go to C:\Windows\SoftwareDistribution and delete everything inside the folder (not the folder itself).
4. Back in Services, right-click Windows Update and select Start.
5. Check for updates again.

Expected result: Windows downloads the update again from scratch and installs it.

7. Check Third-Party Security Software

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Microsoft notes that antivirus or security software from other companies can cause errors while updates install. If you use one:

1. Check the security software maker's website to confirm it supports your version of Windows.
2. Make sure you have its installer and any product key, then temporarily uninstall it from Settings > Apps > Installed apps.
3. Install the Windows update.
4. Reinstall your security software straight away.

Expected result: the update installs while the other security software is removed, and your protection is back on afterward.

8. If the Failing Update Is a Windows Recovery Environment (WinRE) Update

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Check the update's name in Settings > Windows Update > Update history. If it mentions the Windows Recovery Environment, the cause may be space rather than damaged files. Microsoft explains that because of an issue in how these updates report errors, you might see 0x80070643 - ERROR_INSTALL_FAILURE when the real problem is insufficient disk space in the recovery partition.

• Microsoft's Windows 10 WinRE update needs 250 MB of free space in the recovery partition to install.
• Microsoft now says that update isn't offered to PCs whose recovery partition doesn't have enough free space, so check for updates again to see whether it's still listed.
• To see where your recovery environment is installed, open Command Prompt as administrator and run reagentc /info.
• Microsoft also publishes manual instructions to enlarge the recovery partition (KB5028997). They use the diskpart tool to shrink your Windows partition and recreate the recovery partition, so they're for confident users only.

Expected result: the WinRE update either installs after the partition has enough space, or stops being offered.

Still Seeing 0x80070643? What to Try Next

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• Check the date and time: in Settings > Time & language > Date & time, turn on automatic time and time zone, then select Sync now.
• Unplug extra hardware: disconnect storage drives, docks and other devices you don't need, then try again.
• Check the drive for errors: in an administrator Command Prompt, run chkdsk /f C: and restart when asked.
• Read the full guide: How to Fix Windows Update Problems covers more update errors and fixes.