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How to Fix Windows 10 Anniversary Update Error 0xa0000400: Step-by-Step Solutions

Windows 10 Anniversary Update is a major release that brings many new features and improvements. However, some users encounter the error code 0xa0000400 during the update process. This error can prevent the update from installing properly.

Fixing this error may seem complicated, but with the right steps, it can be resolved effectively. This guide will walk you through simple and detailed solutions to get your system updated without hassle.

Each step is explained clearly, even if you are not very tech-savvy. Follow the instructions carefully to avoid any further issues.

By the end of this article, you will understand how to troubleshoot and fix the update error 0xa0000400 on Windows 10 Anniversary Update.

Quick Note Before You Begin

Before diving into the solutions, make sure of the following:

  • Your PC is connected to a stable internet connection. Interrupted downloads can cause update errors.
  • You have enough free disk space. The Anniversary Update requires at least 20 GB free for smooth installation.
  • Disable any third-party antivirus temporarily, as it might interfere with the update process.
  • Ensure your device is plugged into a power source to avoid shutdowns during update.

Step 1: Run the Windows Update Troubleshooter

The Windows Update Troubleshooter is a built-in tool designed to detect and fix common update problems automatically.

  1. Click on the Start menu and select Settings (gear icon).
  2. Go to Update & Security and then click on Troubleshoot from the left menu.
  3. Click on Additional troubleshooters.
  4. Select Windows Update and then click Run the troubleshooter.
  5. Wait for the process to complete and follow any on-screen instructions to fix detected issues.

This step is important because it can automatically repair corrupted update files or settings that cause error 0xa0000400.

Step 2: Clear the Windows Update Cache

Sometimes, corrupted files in the update cache can cause installation errors. Clearing this cache forces Windows to download fresh update files.

  1. Press Windows + R keys to open the Run dialog box.
  2. Type services.msc and press Enter.
  3. In the Services window, scroll down and find Windows Update.
  4. Right-click on it and select Stop.
  5. Now, open File Explorer and navigate to C:WindowsSoftwareDistributionDownload.
  6. Delete all files and folders inside the Download folder.
  7. Go back to the Services window, right-click Windows Update again, and select Start.

Clearing the cache removes temporary files that might be causing the update to fail.

Step 3: Reset Windows Update Components Manually

If clearing the cache does not work, resetting the Windows Update components manually can help fix deeper issues.

Follow these steps carefully:

  1. Open Command Prompt as Administrator. To do this, type cmd in the Start menu, right-click Command Prompt, and choose Run as administrator.
  2. Type the following commands one by one and press Enter after each:
net stop wuauserv
net stop cryptSvc
net stop bits
net stop msiserver
ren C:WindowsSoftwareDistribution SoftwareDistribution.old
ren C:WindowsSystem32catroot2 catroot2.old
net start wuauserv
net start cryptSvc
net start bits
net start msiserver

These commands stop the update services, rename the folders where update files are stored, and then restart the services. Renaming these folders forces Windows to create fresh folders and files for updates.

Step 4: Run System File Checker to Repair Corrupted Files

Corrupted system files can also cause update errors. The System File Checker (SFC) scans and repairs such files automatically.

  1. Open Command Prompt as Administrator again.
  2. Type the following command and press Enter:
sfc /scannow

The scan may take some time to complete. Do not close the window until it finishes.

If any corrupted files are found, the tool will repair them automatically. After the scan, restart your computer and try running the update again.

Step 5: Use the Media Creation Tool to Update Manually

If the previous steps do not fix the error, updating Windows manually using the Media Creation Tool is a reliable alternative.

This tool downloads the update files and installs them outside the normal Windows Update process.

  1. Go to the official Microsoft website and download the Media Creation Tool.
  2. Run the tool and select Upgrade this PC now.
  3. Follow the on-screen instructions to complete the update.

This method bypasses many common update errors and ensures a clean installation of the Anniversary Update.

Alternative Method: Perform a Clean Boot

A clean boot starts Windows with a minimal set of drivers and startup programs. This helps rule out software conflicts that might be causing the error.

  1. Press Windows + R, type msconfig, and press Enter.
  2. In the System Configuration window, go to the Services tab.
  3. Check Hide all Microsoft services to avoid disabling essential services.
  4. Click Disable all to turn off third-party services.
  5. Go to the Startup tab and click Open Task Manager.
  6. Disable all startup items listed here.
  7. Close Task Manager and click OK in the System Configuration window.
  8. Restart your computer and try running the update again.

If the update installs successfully, you can re-enable the services and startup programs one by one to find the conflicting software.

Frequently Asked Questions (FAQs)

What does error code 0xa0000400 mean?

This error indicates that the Windows Update process encountered a problem preventing it from completing. It often relates to corrupted update files or system components.

Can I lose my files during these troubleshooting steps?

No, the steps provided do not delete your personal files. However, it is always recommended to back up important data before performing system updates or repairs.

Is it safe to disable antivirus during the update?

Temporarily disabling third-party antivirus can help avoid conflicts with Windows Update. Just remember to turn it back on after the update is complete.

How long does the update process take?

The duration varies depending on your system and internet speed but generally takes between 30 minutes to an hour.

What if I still get the error after trying all steps?

In that case, more advanced troubleshooting or professional help may be needed. See the “When Nothing Works” section below.

When Nothing Works

If you have followed all the steps above and still face the error 0xa0000400, consider the following options:

  • Perform a System Restore: Restore your PC to a previous point before the update attempt.
  • Contact Microsoft Support: Visit the official Microsoft Support page for personalized help.
  • Reset or Reinstall Windows: As a last resort, you can reset your PC or perform a clean installation. Make sure to back up your data first.

Conclusion

Error 0xa0000400 during the Windows 10 Anniversary Update can be frustrating, but it is usually fixable with the right approach. Starting with simple tools like the Windows Update Troubleshooter and clearing cache can resolve most issues.

If those don’t help, resetting update components, running system scans, or using the Media Creation Tool provide stronger solutions. Performing a clean boot can also uncover hidden software conflicts.

Remember to check prerequisites like internet connection and disk space before updating. In extreme cases, professional support or system restore options are available.

Following this guide step-by-step will increase your chances of successfully installing the Anniversary Update without encountering error 0xa0000400 again.

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