How to fix Windows Defender error code 0x800b0100

Gone are those days when Windows users required third-party programs for protecting their system. Windows introduced the Windows Defender utility tool in a build of Windows 10, and ever since then, many users have stopped using other third-party antivirus programs. The Windows Defender does all that an antivirus program would do by implementing a firewall for the system while ensuring that the system does not fall victim to any malware infection.

But much like other Windows tools, the Windows Defender is also not free of errors. There have been several reports where the users said that they had issues starting the program. Whenever they try to launch the program, they see an error message on the screen that reads the error code 0x800b0100. If you are also encountering this problem on your Windows computer, this article will help you out. Here, we have included the solutions that have solved this particular error code for many Windows users. So without any further ado, let’s get into it.

How to fix Windows Defender Error 0x800b0100?

This error shows up when the user tries to launch the program, and the program won’t start at all. So, fixing this is necessary if you want to maintain the security of your device against any possible threat. You don’t need to try all the solutions mentioned in this article. Just try one solution after the other until you find the solution that solves your problem.

Perform Clean Boot:

Sometimes a third-party program can be the cause behind the Windows Defender not launching on a Windows computer. And performing a clean boot will get rid of this problem as it will disable all the third-party applications that launch when the computer boots up.

Press Windows key + R to open up the Run dialog box.
Enter “msconfig” in the dialog box and click on Ok.
Go to the Services tab in the System Configuration window.
Check the box next to “Hide All Microsoft Services.”
Click on the Disable all button.

Fix: Windows Defender Error 0x800b0100

Now go to the startup tab and click on Open Task Manager.
Right-click on each of the processes that show up and choose the option “Disable” for all of them.
Click on Ok to confirm the changes.
Finally, Restart your computer.

If your Windows Defender starts up without any problems or errors now, then the culprit was definitely one of the third-party applications that you disabled from starting up a while ago. You need to find this particular application and then uninstall it from your computer to let the Windows Defender launch and function without any errors. To find the problematic application, repeat the process mentioned above several times and disable one application after the other until you find the one causing issues for the Windows Defender.

If you are stuck with the error 0x800b0100 even after the clean boot, then try the next solution mentioned below.

Check for any possible malware infection:

Whenever there is a malware infection in your computer, the first thing that it will attack is your device’s security and defense. So the Windows Defender is most likely to be attacked by malware before everything else in your computer. So if you are having problems launching the Windows Defender suddenly, then it is high time you perform a system-wide scan for any possible infection. Install a third-party antivirus program on your computer and run a full scan of your entire system. Don’t just do a quick scan as it does not have many directories of Windows. The full scan will take a while, but it is much more reliable than the quick scan.

If you find an infection, then fix it with your antivirus. You can either delete the file or repair the infected file. If removing the virus or malware from your computer also did not solve the error 0x800b0100 with the Windows Defender, or if you could not find any malware infection, then go ahead with the next possible solution mentioned below.

Check all the Windows Defender services:

Windows Defender tool has several services running in the background that ensure that the program is running without any problems. Check these services and make sure that all of them are running well.

Press Windows key + R to open up the Run dialog box.
Enter “services.msc” in the dialog box and click on Ok.
Find the Windows Defender Service, Windows Defender Advanced Threat Protection Service, and Windows Defender Network Inspection Service.
Right-click on each one of them and choose Properties.
Set the startup type for each of these services as Automatic.
If any of these services are stopped, then right-click on them and choose Start.

Fix: Windows Defender Error 0x800b0100

Again, if that does not work, then right-click on each of these services and choose Restart.

If configuring the services for the Windows Defender also did not solve the error 0x800b0100, try the next solution mentioned below.

Run System File Checker Tool:

System File Checker or SFC is a Windows Utility tool that scans and fixes corrupted system files. You might be facing the error 0x800b0100 in Windows Defender due to a System File corruption issue. And a System File Checker Utility tool should be able to fix it.

Press Windows key + R to open up the Run dialog box.
Type “cmd” in the dialog box and press Ctrl+Shift+Enter.
The UAC window will pop up. Click on Yes here.
The command prompt window will show up now. Enter the following key in the command prompt window and press the Enter key.

sfc/scannow

Let the system file checker process be complete, and then restart your computer.

Now try relaunching the Windows Defender. If you encounter the same error 0x800b0100, try the next solution mentioned below.

Run DISM:

Deployment Image Servicing and Management or DISM is a tool present in Windows for fixing any system-related problems. If the SFC scan could not fix your issue with the Windows Defender, then running the DISM might solve it.

Press Windows key + R to open up the Run dialog box.
Type “cmd” in the dialog box and press Ctrl+Shift+Enter.
The UAC window will pop up. Click on Yes here.
The command prompt window will show up now. Enter the following key in the command prompt window and press the Enter key.

DISM.exe /Online /Cleanup-Image /RestoreHealth

Now, wait for the DISM process to be complete. If you get stuck at a particular percentage for a while, then don’t worry. It is normal for DISM scan to run slow, and in some computers, it might even take an hour or more. At the same time, a powerful machine should be done within minutes.
After the process has completed to 100%, close the command prompt window and restart your computer. If you still see the same error 0x800b0100, try the next solution mentioned below.

Perform a Windows Repair(or clean install):

Performing a Windows Repair will require the Windows installation files with a bootable media device. Windows allows its users to download the latest version of Windows 10 directly from Microsoft’s website. So you should not have any problems downloading the latest version of Windows. If you already have a purchase key for Windows 10, then note it down as it might come in handy after the repair is done.

After downloading all the Windows installation files, create a bootable USB device or CD and move the contents of the Windows installation files onto one of these devices. Then insert the USB device or CD into your computer and let your computer boot up using this bootable device. If your Windows starts up normally, get into the Boot menu by pressing one of the function keys in your keyboard and allow your computer to boot up using the USB drive or CD that you have just inserted with all the Windows installation files in it.

Once your computer boots using the provided bootable device, you will see the installation screen for Windows 10. Follow the on-screen instructions here and allow the windows installation to repair your Windows.

If repairing the Windows does not work, then startup your PC normally, create a backup of everything essential to you, store it in an external storage device, and then use the bootable USB or CD to clean install Windows all over again. A clean install will involve the formatting of the entire computer. So make sure to create a backup before going ahead with the new Windows installation.

After your Windows installation is done, use the Windows activation key that you noted down before and enter it to activate this new installation of Windows. After the fresh installation, the Windows Defender should work without any errors showing up on the screen.

This is the solution for fixing Windows Defender launch error 0x800b0100 on Windows 10. If you have any questions or queries about this article, then comment down below, and we will get back to you. Also, be sure to check out our other articles on iPhone tips and tricks, Android tips and tricks, PC tips and tricks, and much more for more useful information.