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 parties. However, you will encounter some Windows Update Center error codes during the update process. One is error code 646 from the Windows Update Center. This happens when users try to install updates for Microsoft Office. The Windows installer detects the problem during the process. According to 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 for their Microsoft Office, they get the following error message (*Update Error).

I found a bug:

Code 646 The Windows Update Center has detected an unknown error.

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

Running Windows Update Center Troubleshooting


Step one. Press the Windows + R keys to open the start window.

Step two. Enter the control panel and press the Enter key to open the classic control panel interface.

Step three: Enter a troubleshooter into the search bar at the top right of the screen.

Step four: Click the Troubleshooting item in the list of search results.

Step Five: In the System and Security section, click Windows Update Troubleshooting Center to open the Windows Update Troubleshooting Center.

Step six: Click on Advanced.

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Step seven: Select the check box for the automatic repair application.

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

Step 9 : Restart your computer.

January 2024 Updated:

We now recommend that you use this tool to correct the error. The tool also corrects common computer errors, protects against file loss, malware and hardware failures, and optimizes your PC for optimal performance. With this software you can quickly solve problems on your PC and prevent others from having problems:

  • Step 1 : Download the PC Repair and Optimization Tool (Windows 10, 8, 7, XP, Vista – Microsoft Gold Certified).
  • Step 2 : Click on the Start scan button to detect problems in the Windows registry that may cause PC problems.
  • Step 3 : Click the Fix All button to fix all issues.


Disable firewall

Window-wall-on-stop .

If you have a firewall installed, disable it for a while and download the necessary updates for Windows and Microsoft Office. Sometimes the Firewall blocks important updates for Windows. If this does not solve the problem, go to the next step.

Install the update from the Windows Update Center directory.

If the Windows Update Center troubleshooter could not find and fix the local WU component that prevents the installation of some Windows updates, you can bypass this component completely if necessary.

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

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In most cases, this will confirm that error code 646 has occurred, with subsequent updates:

  • KB972363.
  • KB973709
  • KB972581
  • KB974234
  • KB974810

Delete the AppData key with the registry editor

Step one: Press the Windows + R keys to open the start window.

Step two: Type regedit and press the Enter key to open the registry editor. Click Yes to grant administrator rights when prompted to manage the user account.

Step three: Go to the next place:
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 four: Double-click on the AppData registry section and make sure the value is% USERPROFILE% AppData Roaming. If the value is different, change it and click OK to save the changes.

Step Five: Restart your computer.

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CCNA, Web Developer, PC Convenience Store

I am a computer enthusiast and a practicing computer professional. I have years of experience in computer programming, troubleshooting and hardware repair. I specialize in web development and database design. I also have a CCNA certification in network design and troubleshooting.

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