How to Fix Windows Defender Error 0x800b0100

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When you start Windows Defender, you may receive an error with the error code 0x800b0100, which prevents you from enabling Windows Defender, and your Windows Defender remains disabled.

The 0x800b0100 error can be caused by several things. It can occur because your system is infected, an antivirus program is causing the problem, or system files are damaged. Since there can be several reasons, there are also different solutions to this problem. Depending on the cause of the error, each method may work for you. Therefore, try one of the methods listed below until the problem is solved.

Check your Windows Defender service

  • Press Windows + R
  • Enter msconfig
  • Search in Windows Defender
  • Double-click the following items:
  • Windows Defender Service
  • Advanced Windows Defender Threat Protection Service
  • Windows Defender Network Inspection Service
  • Make sure that the start type is set to Automatic and the service is started.

Scan your PC for malware

Ironically, this Windows Defender may be caused by a pre-existing infection on your Windows 10 PC. So all you need to do is install a very good third-party antivirus program to perform a complete scan and cleanup of your Windows system.


DISM (Deployment Image Servicing and Management) is a tool that can be used to correct damaged system files. It is a built-in tool that is pre-installed in Windows. This means that you do not need to download any third party software and you can simply run commands from cmd.

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  • Hold down the Windows key and press X
  • Select the command prompt (Admin)
  • Enter dism.exe /Online /Clean Image /Restorehealth and press Enter.

Configure the Windows Defender service to start automatically

  • Press the Windows + R key, type services.msc and press Enter.
  • Locate the Windows Defender antivirus service and double-click it.
  • Open the Startup Type and set it to Automatic.
  • Click Apply and OK to save the changes.

Performing a Clean Boot


You must try to boot the PC properly to solve the problem with Windows Defender error code 0x800b0100. This will help you determine if there is a malicious application on your system. To do this, follow the steps below:

  • Hold down the Windows key and press R, type msconfig and press Enter.
  • Go to the Services tab and select the options to hide all Microsoft services.
  • Click “Disable All” and open “Startup”.
  • Select the Task Manager and right-click on each item it contains and select Disable.
  • Then press OK and restart your computer.

When the restart process is complete, restart the Windows Defender software to see which application caused the malfunction. After detecting this particular program, activate all other processes except this one.

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