How to Fix Windows Update Error Code 646

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Windows Update Center is a handy feature that users often use to install updates not only from Microsoft, but also from third-party vendors. However, you will encounter a number of Windows Update Center error codes during the update process. The Windows Update Center error code 646 is one of them. This happens when users try to install updates for Microsoft Office. The Windows installer detects the problem during the process. Based on user feedback, code 646 is exclusive to Windows 7 and Windows 8.1.

When users open the Windows Update Center and try to install an update to their Microsoft Office, they see the following error (* Update Error).

Found the error:

Code 646 The Windows Update Center found an unknown error.

You see this error and realize that the requested or automatic update has failed. You should take immediate action to resolve the problem yourself. In the content below, I will show you some useful methods to fix the Windows 646 error code.

Run the Windows Update Center Troubleshooter


Step 1. Press the Windows + R key to open the startup window.

Step 2. Type control and press Enter to open the classic control panel interface.

Step 3: Enter troubleshooting in the search bar in the upper right corner of the screen.

Step 4: Click the Troubleshooting entry in the search results list.

Step 5: Under System and Security, click Windows Update Center Troubleshooting to open the Windows Update Center Troubleshooter.

Step 6: Click Advanced.

Step 7: Check the checkbox to automatically apply the repair.

Step 8: Click Apply this fix and follow the instructions on the screen.

Step 9: Restart your computer.

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Disable Firewall


If you have a firewall installed, disable it for a while and download the necessary Windows and Microsoft Office updates. Sometimes the firewall blocks important updates for Windows. If that doesn’t solve the problem, go to the next step.

Install an update from the Windows Update Center directory.

If the Windows Update Center Troubleshooter couldn’t find and fix the local WU component that’s preventing you from installing certain Windows updates, you can bypass that component completely if necessary.

As some affected users have reported, you can probably install the failed updates yourself by downloading them from the Microsoft Update Center catalog and installing them manually. Sure, it’s a bit tricky (especially when multiple updates fail), but it’s still better than running an outdated computer.

In most cases, it will confirm that you encountered error code 646 with the following updates:

  • KB972363.
  • KB973709
  • KB972581
  • KB974234
  • KB974810

Remove the AppData key using the registry editor

Step 1: Press the Windows + R key to open the Startup window.

Step 2: Type regedit and press Enter to open the registry editor. Click Yes to grant administrator rights when prompted by User Account Management.

Step 3: Go to the following location:
HKEY_USERS \ .DEFAULT \ Software \ Microsoft \ Windows \ CurrentVersion \ Explorer \ User shell folder
HKEY_CURRENT_USER \ Software \ Microsoft \ Windows \ CurrentVersion \ Explorer \ User shell folder
HKEY_CURRENT_USER \ Software \Microsoft \Windows \CurrentVersion \ Explorer \ User shell folder

Step 4: Double-click the AppData registry section to make sure the value is% USERPROFILE% \ AppData \ Roaming. If the value is different, change it and click OK to save the changes.

Step 5: Restart your computer.

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