How can I fix Windows Defender Error Code 0x800b0100?

The windows defender error code 0x800b0100 indicates that the system was unable to find a required file. This file may be corrupt or missing. This error code can also happen if there is a problem with the digital signature of a file.

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• error code: (0x800b0100)
• windows defender error code 0x800b0100

• Restart your computer and try running Windows Defender again
• Run the Windows Defender offline scan
• Check for updates to Windows Defender
• Temporarily disable your antivirus program and try running Windows Defender again
• Add an exclusion to Windows Defender

1. Restart your computer and try running Windows Defender again

1. First, open your computer's Start menu and search for "Restart"
2. Once you have located the Restart button, click on it to start the restart process.
3. As your computer starts up, wait until it finishes restarting before trying to run Windows Defender again.
4. If Windows Defender still fails to start, please follow our troubleshooting guide below. If Windows Defender still fails to start after following our troubleshooting guide, please contact our support team for further assistance.

2. Run the Windows Defender offline scan

1. Open the Windows Defender Offline Scanner by clicking on the start button, type "windows defender offline scan" in the search bar and press enter.
2. Click on the "Scan Now" button to start the scan.
3. When the scan is finished, a report will be generated and will show the results of the scan.
4. If the scan results show that there is a problem with windows defender, then follow the instructions to fix the problem.

3. Check for updates to Windows Defender

1. Launch the Windows Defender application.
2. Click on the “Update” button on the top left corner of the window.
3. On the “Update” screen, click on the “Check for updates” button.
4. If there are any updates available, they will be listed on the “Update” screen.
5. Click on the “Install updates” button to install the updates.
6. Once the updates are installed, click on the “Close” button on the “Update” screen.

4. Temporarily disable your antivirus program and try running Windows Defender again

1. Open Control Panel and click on System and Security.
2. Under System and Security, click on Windows Defender.
3. On the Windows Defender tab, under the Action column, click on the Settings button.
4. On the Settings window, under the Windows Defender Protection category, click on the Temporarily disable button.
5. On the Temporarily disable window, click on the OK button.
6. Under the Action column, click on the Windows Defender Protection category.
7. On the Windows Defender Protection category window, under the Windows Defender Protection status column, click on the Enable button.
8. On the Enable window, click on the OK button.
9. Under the Action column, click on the Windows Defender Protection category.
10. On the Windows Defender Protection category window, under the Windows Defender Protection status column, click on the OK button.

5. Add an exclusion to Windows Defender

1. Open Windows Defender and click on “Exclusions” on the left-hand side.
2. In the “Exclusions” window, click on the “New Rule” button.
3. In the “New Rule” window, enter the following information:

• Name: “My Exclusion”
• Type: “Windows Defender”
• Action: “Exclude”
• Comment: This is an exclusion for Windows Defender.

4. Click on the “Add” button.
5. In the “Add Exclusion Rule” window, click on the “OK” button.
6. Windows Defender will now exclude the My Exclusion rule from the Windows Defender protection.

If you didn't find success with an option above, then try:

1. Turn off real-time protection in Windows Defender.
2. Uninstall and reinstall Windows Defender.