What is Error 0x80071a91?

Error 0x80071a91 is a common Windows error code that primarily indicates issues related to the Windows Update database, preventing the operating system from successfully downloading, installing, or configuring updates. This error can disrupt the normal functioning of your system's update process, leaving it vulnerable or lacking the latest features.

This error often arises when the files or services responsible for managing Windows updates become corrupted, inaccessible, or encounter conflicts. Resolving it typically involves troubleshooting the underlying components of the Windows Update service.

Common Symptoms of Error 0x80071a91

When encountering error 0x80071a91, users typically observe one or more of the following symptoms:

Failed Windows Updates: Updates repeatedly fail to install, often rolling back changes.
Update Loop: The system attempts to install updates, fails, reverts changes, and then tries again in a loop.
Slow System Performance: General system slowdowns, especially during update attempts.
Error Messages: Specific error messages mentioning "0x80071a91" appear during update processes.
Inability to Install Features: Difficulty installing new Windows features or optional updates.

Why Does Error 0x80071a91 Occur?

Several factors can lead to the 0x80071a91 error, most of which center around the integrity and functionality of the Windows Update components:

Corrupted Windows Update Database: The most common cause, where essential files within the update database are damaged or missing.
Corrupt System Files: Underlying corruption in core Windows system files can interfere with update operations.
Software Conflicts: Third-party antivirus software or other applications might interfere with Windows Update services.
Network Issues: Unstable internet connection or network configuration problems can prevent update downloads.
Malware or Virus Infection: Malicious software can corrupt system files and hinder update processes.
Insufficient Disk Space: Although less common for this specific error, lack of adequate storage can prevent updates from being processed.

How to Fix Error 0x80071a91

Resolving error 0x80071a91 often involves a series of troubleshooting steps, starting with simpler fixes and progressing to more advanced solutions.

Initial Troubleshooting Steps

Before attempting complex fixes, try these basic yet effective solutions:

Restart Your Computer: A simple restart can often resolve temporary glitches affecting update services.
Run the Windows Update Troubleshooter:
- Go to Settings (Windows key + I).
- Navigate to System > Troubleshoot > Other troubleshooters.
- Find Windows Update and click Run.
- Follow the on-screen instructions to allow the troubleshooter to identify and fix problems.

Advanced Solutions

If the initial steps don't resolve the issue, consider these more in-depth solutions.

Reset Windows Update Components Manually: This process involves stopping update-related services, clearing the update cache, and restarting the services.
- Open Command Prompt as an administrator.
- Stop the BITS, Windows Update, and Cryptographic services by typing these commands and pressing Enter after each:
```
net stop bits
net stop wuauserv
net stop appidsvc
net stop cryptsvc
```
- Delete the Qmgr*.dat files:
```
Del "%ALLUSERSPROFILE%\Application Data\Microsoft\Network\Downloader\qmgr*.dat"
```
- Clear the Windows Update cache by renaming the SoftwareDistribution and Catroot2 folders:
```
Ren %systemroot%\SoftwareDistribution SoftwareDistribution.bak
Ren %systemroot%\system32\catroot2 catroot2.bak
```
- Reset the BITS and Windows Update services to their default security descriptors:
```
sc.exe sdset bits D:(A;;CCLCSWRPWPDTLOCRRC;;;SY)(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;BA)(A;;CCLCSWLOCRRC;;;AU)(A;;CCLCSWRPWPDTLOCRRC;;;PU)
sc.exe sdset wuauserv D:(A;;CCLCSWRPWPDTLOCRRC;;;SY)(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;BA)(A;;CCLCSWLOCRRC;;;AU)(A;;CCLCSWRPWPDTLOCRRC;;;PU)
```
- Re-register the BITS files and Windows Update DLLs. (This is a longer list, often better done via a script or by searching for a comprehensive list of DLLs for your OS version, but for brevity, a common approach is to skip this if the above renaming works, or to use a dedicated reset script.)
- Start the BITS, Windows Update, and Cryptographic services:
```
net start bits
net start wuauserv
net start appidsvc
net start cryptsvc
```
- Restart your computer and try Windows Update again.
Run System File Checker (SFC) and DISM: These tools help repair corrupted system files that might be affecting Windows Update.
- Open Command Prompt as an administrator.
- Run SFC by typing: sfc /scannow and press Enter. Let it complete.
- If SFC finds errors it cannot fix, or if the problem persists, run DISM (Deployment Image Servicing and Management):
```
DISM /Online /Cleanup-Image /RestoreHealth
```
- Restart your computer after the scans are complete.
Perform a Clean Boot: A clean boot starts Windows with a minimal set of drivers and startup programs, helping to identify software conflicts.
- Search for msconfig and open System Configuration.
- Go to the Services tab, check Hide all Microsoft services, and then click Disable all.
- Go to the Startup tab, click Open Task Manager, and disable all startup items.
- Restart your computer. If the update works, re-enable services and startup items gradually to pinpoint the culprit.
Manually Download and Install Updates: If all else fails, you might be able to manually download the problematic update from the Microsoft Update Catalog.
- Note down the KB (Knowledge Base) number of the failed update.
- Visit the Microsoft Update Catalog website.
- Search for the KB number.
- Download the correct version for your operating system and architecture (32-bit or 64-bit).
- Run the downloaded file to install the update.

Summary of Solutions

Solution Category	Action	Purpose
Initial Steps	Restart Computer	Clear temporary glitches
	Run Windows Update Troubleshooter	Automatically detect and fix update problems
Advanced Fixes	Reset Windows Update Components	Rebuild the update database and services
	Run SFC and DISM	Repair corrupted system files
	Perform a Clean Boot	Identify software conflicts
	Manually Download Updates	Bypass the automatic update process for specific fixes

By systematically applying these solutions, you can effectively address error 0x80071a91 and restore your system's ability to receive crucial Windows updates, ensuring your device remains secure and up-to-date.