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How to fix Windows Defender service won’t start on Windows 10?

By Eunice Samson | June 9, 2018 |

greater than 5 minutes

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Windows 10 has a built-in anti-virus program that is trusted by millions of users across the globe. It is reliable enough to protect computers from common threats and attacks. However, many users have reported that at times, it can be difficult to launch the service. In some cases, the issue is accompanied by an error message that appears on the screen. Here are some of the common scenarios related to the problem:

  • Windows Defender service won’t start error 577 – As we’ve mentioned, the issue can come with an error message. You can resolve this by ensuring that your third-party anti-virus is not interfering with Windows Defender.
  • Windows Defender service not starting on Windows 10, 8.1, and 7 – Many users reported that the problem can occur on various versions of Windows, including 10, 8.1, and 7. It is worth noting that most of the methods we included in this article can also be used for older versions of Windows. So, feel free to give them a try.
  • Windows Defender Security Center failed to open – There are some users who reported that they couldn’t open Windows Defender Security Center at all. You can resolve this issue by installing the latest updates.
  • Windows Defender service keeps stopping – It is possible that profile corruption is behind this problem. So, you’d have to create a new user profile and check if that gets rid of the issue.

So, how can you protect your PC when Windows Defender service keeps stopping? Thankfully, we’ve got a collection of workarounds for this issue. So, if you want to know how to fix Windows Defender service won’t start on Windows 10, continue reading this article and follow our methods!

Method 1: Disabling or removing your third-party anti-virus programs

In some cases, third-party anti-virus can interfere with Windows Defender and cause different technical issues. So, the first solution you can try is disabling your other security programs. If that does not work, it would be best to completely remove them. Restart your PC and try launching Windows Defender again to see if the issue has been resolved.

Some people do not feel comfortable relying on Windows Defender alone for their security needs. So, if you were able to fix the issue by removing your third-party anti-virus, we recommend switching to a more reliable anti-virus. When you go online, you will find several good security programs, but we highly recommend Auslogics Anti-Malware for many great reasons.

For one, it catches threats and attacks that Windows Defender would miss. What’s more, it is designed to be compatible with Windows 10. Needless to say, it will not conflict with your main anti-virus. So, you can keep Windows Defender while reinforcing your computer’s security with the help of Auslogics Anti-Malware.


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Method 2: Installing the latest Windows updates

Some users reported that they had been able to fix the issue simply by installing the latest updates. When you keep your system updated, you can make sure that everything on your computer will run smoothly. In general, Windows 10 automatically downloads and installs updates in the background. However, it is possible for the system to miss an update or two. So, it is always best to manually check for updates by following the instructions below:

  1. Launch the Settings app by pressing Windows Key+I on your keyboard.
  2. Click Update & Security.
  3. Click the Check for Updates button.

Check for updates to protect and patch your system.

Once you’ve done that, Windows will check if there are updates available for your PC. The system will automatically download them in the background. You can restart your computer to install these updates.

Method 3: Running an SFC scan

It is also possible that file corruption is the reason why Windows Defender won’t start. Thankfully, you can resolve this issue by running an SFC scan. To do this, simply follow the steps below:

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  1. On your keyboard, press Windows Key+X. From the list, select Command Prompt (Admin) or Powershell (Admin).
  2. Once Command Prompt is up, type “sfc /scannow” (no quotes), then hit Enter.An SFC scan will check your system for system file corruption.
  3. The program will start scanning your system, repairing damaged or corrupt files. The process may take a while, and it is important that you avoid interrupting it.

Once the scan is complete, check if the issue has been resolved. If you still can’t get Windows Defender to run, it would be advisable to try running a DISM scan. Just follow the instructions below:

  1. Click the Search icon on your taskbar.
  2. Type “command prompt” (no quotes).
  3. Right-click Command Prompt on the results, then select Run as Administrator.
  4. Once Command Prompt is up, paste the following text:
  5. DISM /Online /Cleanup-Image /RestoreHealth

Method 4: Cleaning your registry

Corrupted or damaged registry entries can also be the reason why Windows Defender service won’t start. So, you have to locate the problematic entries, then remove or fix them. It is worth noting that this task can be tedious and complicated to perform manually. Moreover, you must be extra cautious because even one mistake can damage your system. So, your best bet is to automate the process, using a reliable tool like Auslogics Registry Cleaner.

Just by clicking a button, you will make this program deeply scan your registry and look for missing, damaged, and corrupted entries. The best part is, Auslogics Registry Cleaner takes care of all problematic entries—not just the ones that caused the Windows Defender issue. So, once the process is complete, you can expect your computer to perform smoothly and faster.

Keep your registry neat and tidy.

Method 5: Checking your environment variables

Your system uses environment variables to easily access certain directories. However, it is possible that you or a third-party application modified them, causing the issue with Windows Defender. Don’t worry because you can fix this by following the instructions below:

  1. Go to your taskbar and click the Search icon.
  2. Type “advanced system settings” (no quotes), then hit Enter.
  3. Near the bottom of the System Properties window, you will see an Environment Variables button.
  4. Look for the %ProgramData% variable and make sure that it is set to C:\ProgramData. Correct the variable accordingly.

Method 6: Creating a new user account

One of the options you can try is to create a new user account. It is possible that the Windows Defender service is not starting because your user account has been corrupted. So, make sure you follow the steps below:

  1. On your keyboard, press Windows Key+S.
  2. Type “settings” (no quotes), then hit Enter.
  3. Go to Accounts.
  4. On the left pane, select Family & Other People from the list.
  5. Go to the right pane, then click Add Someone Else to this PC.
  6. Select ‘I don’t have this person’s sign-in information.’
  7. Choose ‘Add a user without a Microsoft account.’
  8. Type your preferred user name, then click Next.
  9. Switch to the new user account and check if the problem persists.

Do you have suggestions for resolving this issue?

Share your ideas in the comments below!

Fed up with your slow PC? Tired of waiting for Windows to start up? Take a look at the most common reasons behind poor performance and the best ways to deal with them here.


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