Windows Defender Won't Start in Windows 10 Fix

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Philippe Gloaguen

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il Windows Defender is a security program that comes with Windows to protect your PC from threats like viruses, malware, spyware, and more. Sometimes it can happen that Windows Defender doesn't start at all. There are several reasons why Windows Defender isn't working in Windows 10, but it's hard to determine exactly what the reason is.

Here, we have compiled a list of solutions that will help you get Windows Defender working on your PC again. Find out how to fix Windows Defender not starting problem in Windows 10:

Solution 1: disable / uninstall antivirus

It was found that the reason Windows Defender won't start in most cases was because of the presence of antivirus software on the PCs. Antivirus interferes with important Windows settings which could cause conflicts like these. If you really want to run Windows Defender on your PC, the first thing to do is to disable Antivirus on your PC. If that doesn't work, you'll need to uninstall the antivirus program from your PC.

Remember to uninstall your antivirus software using a dedicated software removal tool. These tools ensure they remove software leftovers, such as junk files, and undo unnecessary changes.

After uninstalling the antivirus, restart your PC and try to start Windows Defender. If it doesn't start, try the next method.

Solution 2: update Windows 10

According to many users, they were unable to start Windows Defender because the version of Windows 10 installed on their PC was out of date. If you have an older version of Windows 10 installed on your PC, update it and check for the problem.

Step 1: Open the settings the application in Windows by pressing the key Win + me keys together. Now select the file Update and security option in the Settings menu.

Step 2: A new configuration menu will open. Here, from the left panel, select the file Windows update option. Now go to the right pane and click Look for updates button.

Now the program will scan the Windows server to check if a new Windows 10 update is available. You will be prompted for the same thing; Follow the onscreen instructions to complete the Windows update. Once the update is complete and your PC restarts, you will be able to run Windows Defender.

Solution 3: Run the SFC scan

SFC Scan is a Windows command line utility that searches for corrupted or damaged system files on your PC. Once the files are found, the tool also fixes them. Windows Defender may not be able to run due to system file problems. These are the steps:

Step 1: Open Command Prompt on your PC with elevated privileges. To do this, press Win + WILL, then in the search bar type cmd. Now right click on the file Symbol of the system search result and click Run as administrator option.

Step 2: The command prompt window will open. Type the following command there and hit the Log in key:

sfc / scannow

Let the scan run; it may take a while. Once the scan is complete, restart your PC and try to run Windows Defender.

Solution 4: run a registry cleanup

Another way to deal with Windows Defender failing to start is to run a registry cleanup. There are many third-party tools available that can help you clean the registry on your PC. Performing a registry cleanup will take care of unwanted and unnecessary entries in the registry.

You can try CCleaner or any of these CCleaner alternatives to perform registry cleanup.

Solution 5: Check Windows Defender services

There are a few services in Windows that are responsible for running Windows Defender. You will need to check if they are running and restart them, or you may need to change their properties. That is how:

Step 1: Open the Services utility. For this, press the button Win + R keys, then in the Run box that opens, type Servicesmsc and press the button Log in key.

Step 2: A Services list, look for the following services and make sure they are running:

  • Security center
  • Windows Defender Advanced Threat Protection
  • Windows Defender Firewall
  • Windows Defender Antivirus Network Inspection Service
  • Windows Defender Antivirus Service

Once you find these services, make sure they are running by checking the file State section. If one of these services is not running, select the service and press the key Home button.

3 pass: In this step you will need to restart any services that are already running. To do this, right-click on the service and select the file Restart option and check if the defender starts; if not, go to the next step.

Phase 4: Double-click on each of these services to open the File Properties window. In the Properties window, make sure Start type is selected as Automatic. If the startup type is set to something else, change it to Automatic. Click on ok after making the changes and close the Services window.

Now restart your PC and check if the problem is solved.

Solution 6: Change the local group policy

If Windows Defender doesn't start, it may be disabled by Local Group Policy on your PC. To make sure this is not the case, you will need to access the Local Group Policy Editor. Follow the steps below:

Step 1: Open the run by pressing the button Win + R keys, then type gpedit.msc and click ok button.

Step 2: The Local Group Policy Editor window will open. Here, go to the left panel and navigate to the following location:

Computer Configuration> Administrative Model> Windows Components> Microsoft Defender Antivirus

3 pass: Go to the right pane and double click Disable Microsoft Defender Antivirus option. A new window will open; here, make sure the Not configured the option is selected. Click on ok and exit the Local Group Policy Editor window.

Now restart your PC and see if you can start Windows Defender.

Solution 7: Change the permissions of the Microsoft directory

If the Microsoft directory on Windows does not have the proper permissions, you may not be able to start Windows Defender. These are the steps to follow to make the changes:

Step 1: Open File Explorer on your PC and go to the following address:

This PC> Local Disk (C :)> ProgramData

There, locate the file Microsoft folder, right click on it and select the folder Property option.

Step 2: In the Properties window, go to the file Safety tab and click Advanced option.

3 pass: In the new window that opens, look for inherited permission entries. For this, see the Inherited from status of authorization entries. If a permission has been inherited, click Change permissions option and remove the permission entry.

After this save your changes and exit File Explorer, restart your PC and check if you can start Windows Defender.

Solution 8: perform a clean boot

As many users have reported, performing a clean boot on their PC helped them get rid of this problem. It is quite a simple process and has helped many users to get rid of various Windows errors and problems such as Windows Defender not starting.

Here's how to restart your PC in clean boot mode in Windows 10.

After performing a clean boot, check if you can run Windows Defender.

Solution 9: Create a new user account

Here is another solution you can try if none of the above solutions worked for you. Go ahead and create a new user account in Windows. After creating the new account, log out of your current user profile and log in with the new profile.

Here's how to create a new local user account in Windows 10.

If Windows Defender doesn't start using your new user profile, you can continue using your original profile. If the solution works, we recommend that you use the new account.

Solution 10: Perform a registry fix

To fix the problem that Windows Defender won't start, you can run a registry fix on your PC. These are the steps to follow:

Step 1: Open the Run box by pressing Win + R keys. gender regedit in the Run and select box ok.

Step 2: In the Registry Editor, go to the left pane and navigate to the following path:

HKEY_LOCAL_MACHINE> SOFTWARE> Microsoft> Windows Defender

Now, right-click on the file Windows Defender folder and click Permissions option.

3 pass: In the Windows Defender Permissions window, select the file Advanced option.

Phase 4: In the new window that opens, select the file Modify option available right next to the SYSTEM option.

5 pass: The Select User or Group window will open. Here in the Enter the name of the object to select Section type CEO and click ok option.

6 pass: You will return to the previous window. Here, select the file Replace owner on subcontainers and objects box. After that, go to Entries of authorization section and double-click the file CEO registration.

7 pass: In the Permission Entry window that opens, select the file Total control check box and click ok. Again, press ok then close Registry Editor.

8 pass: Download the following ZIP file: DefenderFix. Unzip the ZIP file and run the DefenderFix.reg file which you will find in the unzipped folder. You will be asked if you want to make the changes; Please select Yup.

Now restart your PC and check if Windows Defender is starting up.

Solution 11: In-place upgrade of Windows 10

Performing an in-place upgrade of Windows 10 may be the last resort to get rid of the Windows Defender not starting issue. An in-place upgrade means reinstalling Windows 10 on the currently installed operating system to replace system files. During the update, you can choose whether to keep all files on your PC.

Go ahead and download the file Windows Media Creation Tool on your PC.

Run the installation and select the file Update this PC now option.

Then select the file Download and install updates (recommended) option.

Windows will now download the files required for the update to your PC.

Now follow the onscreen instructions and proceed with the installation. When prompted, be sure to select the file Keep files and apps personal option.

Now a new version of Windows 10 will be installed on your PC. You will be able to start Windows Defender on your PC.


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