How to fix Windows Update error code 66a

The Windows Update error code 66a is a common error issue that has been reported in several versions of the Windows operating system. The prime reasons for the said error include, a malware or virus attack as well as can possibly result in corrupt or incomplete install of .NET framework software and the Windows registry corruption.

FIXES: Windows Update error code 66a

The Windows Update error code 66a commonly appears when the .NET framework is running or during the Windows shutdown/startup process. If you are also a suffered user who is trying to get rid of the said error, then the guide below can help you. Have a look and try the fixes to check whichever suits you the best.

Windows Error

FIX 1: Run SFC scan:

Running an SFC scan is possibly the first solution you can try to get rid of the Windows Update error code 66a. For running the SFC scan, follow the steps given below:

  • Firstly, go to the desktop search bar, type cmd, and launch the Command Prompt window. Make sure you launch it with administrator access.Fix: Notifications Banners Not Showing on Windows 10
  • Now inside the Command Prompt window, type sfc /scannow and then press Enter.
  • Now let the scanning process gets complete on its own.
  • Further, restart your computer and check whether the said issue got resolved or not.
  • Alternatively, you can also use a dedicated tool to check for system file corruption.

FIX 2: Scan your computer for malware:

As per some of the suffered users, scanning their computers for Malware also helped them in order to get rid of the Windows Update error code 66a. You can also try the same and check whether it helps or not.

There are multiple Malware scanning tools available online that are free and safe to use. Consider using a trusted one amongst them.

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FIX 3: Perform a clean boot:

At times some .NET framework-dependent applications can create a software conflict resulting in the Windows Update error code 66a. Such applications can run in the background when you start your computer every time. Thus, here the best solution is to perform a Clean Boot. For doing so, follow the steps given below:

Now Before you begin with the steps, make sure you are logged in with the administrator access.

  • Firstly, make sure that you are logged in to your Computer with administrator access.
  • Now navigate to the Start menu, type msconfig, and launch the System Configuration window. Make sure you launch it with administrator access.
  • Inside the System Configuration window, navigate to the Service tab from the vertical menu, and there down below, click on the tick box before the option Hide all Microsoft service.
  • Further, click on the Disable all tab.
  • Now again, from the vertical menu, navigate to the Startup tab and then click on the link stating Open Task Manager.
  • Inside the Task Manager window, navigate to the Startup tab from the vertical menu, right-click on the problematic entry on the list below and select Disable.
  • Once done, exit the Task Manager window and then navigate back to the System Configuration window.
  • Here click on OK.
  • Lastly, restart your computer and then check whether the said issue got resolved or if it persists.

FIX 4: Rerun Windows update:

The Windows Update error code 66a can also be a result of an incomplete Windows update.

Windows update can be disrupted or halted due to various reasons; therefore, the user must ensure to rerun the Windows update and make sure the process gets completed swiftly. For rerunning the Windows update, follow the steps given below:

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  • Firstly, go to the desktop search bar, type update, and then open the relevant search result.
  • Now inside the Windows update screen, click on the Check for Updates tab and let the updating process get completed on its own.
  • Finally, restart your computer to make the latest installation applicable.
  • Once done, check whether the said issue got resolved or if it persists.

FIX 5: Reinstall .NET Framework:

As discussed earlier as well, .NET Framework is one of the main triggers for the Windows Update error code 66a. Thus, the best solution is to reinstall the .NET Framework and check whether it resolved the said error or not. For doing so, follow the steps given below:

  • Firstly, go to the desktop search bar, type Control Panel and launch the relevant search result.
  • Now inside the Control Panel window, navigate to Programs and Feature.
  • On the next list, scroll down the installed programs and locate .NET Framework amongst them.
  • Once found, click over the .NET Framework program, then select the Uninstall button. Further, follow the on-screen instructions to complete the uninstallation process.
  • Now restart your computer.
  • After that, navigate to the official website and download the .NET Framework.
  • Further, double-click on the executable file and follow the prompts to install the .NET framework.

Note: Consider downloading several versions of the .NET framework, preferably the recent one.

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FIX 6: Revert Windows update changes:

Another procedure that you can try in order to get rid of the Windows Update error code 66a is revert Windows update changes. For doing so, follow the steps given below:

  • Firstly, press Windows + I all together, and it will launch the Settings app on your screen.
  • Now inside the Settings screen, navigate to Update & Security, and then from the left-pane menu, click on Recovery.
  • On the right-pane menu, under the Go back to the previous version of Windows 10 section, click on the Get Started tab.
  • Keep your files and then start the resetting process.
  • Once done, check whether the said issue got resolved or not.

FIX 7: Run system restore in safe mode:

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As per a few suffered users, running System Restore in Safe mode helped them in resolving the Windows Update error code 66a. For doing so, follow the steps given below:

  • To begin with, shut down your computer and then start it again.
  • Now navigate to the Run in Safe Mode and then press Enter.
  • Navigate to Start, then type System Restore, and then press Enter.
  • Follow the prompts and revert back to a restore point (date) when the said issue did not exist.
  • Once the process gets completed, restart your computer.

FIX 8: Use a dedicated Cleaning Software:

If none of the above-mentioned fixes helped you, then, at last, consider using dedicated Cleaning Software. Apart from them, you can also use other third-party registry cleaners.

As discussed earlier in the article, the Windows Update error code 66a can result in Malware or virus infection; thus, it must not be taken lightly. As and when you encounter the said error, make sure you follow the essential measures to resolve it at the quickest.

Once you apply the above-mentioned methods, the Windows Update error code 66a will eventually get resolved, and you will be able to use your system and dedicated programs swiftly all again. If you have any queries or feedback, please write down the comment in the below comment box.

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