FIX: Windows Defender an unexpected problem occurred error

Madalina Dinita
by Madalina Dinita
Managing Editor
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  • Windows Defender is the first line of defence against virus and malware. Please read our article below for plenty of solutions regarding your problem.
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How to fix Windows Defender an unexpected problem occurred

More and more Windows Defender users are reporting they can’t turn on Microsoft’s built-in antivirus program due to various errors:  some of them can’t install the latest updates, while others can’t get the software to perform a quick scan.

Today, we’re adding a new issue on the list, as many users have reported they can’t turn on the real-time protection feature in Windows Defender due to the An unexpected problem occurred error.

There is no particular error code for this error, only a pop-up window asking users to install the latest updates.

Windows Defender offers solid protection, but many users reported An unexpected problem occurred while trying to start Windows Defender. There are other issues that can affect Windows Defender and these are some of the most common ones:

  • Windows Defender unexpected error sorry we ran into a problem – Sometimes you might get this error message while trying to start Windows Defender. If this happens, be sure to remove all files associated with your antivirus and check if that solves the problem.
  • Windows Defender security center not working – If you encounter this issue, the problem might be your services, so be sure to reset them and check if that helps.
  • Windows Defender unexpected error please try again – This is another common problem that can occur in Windows 10. If you encounter this problem, be sure to update Windows 10 and check if that solves the issue.
  • Windows Defender keeps stopping – Many users reported that Windows Defender keeps stopping on their PC. If you encounter this problem, be sure to check your registry.

For the time being, Microsoft’s Support engineers haven’t replied to this thread, and we couldn’t find a specific solution for this error either.

Fortunately, there are some general workarounds available to fix common Windows Defender issues, and we suggest you try them out, for lack of a better solution. Maybe one of the workarounds listed below can solve this issue.

An unexpected problem occurred error in Windows Defender

Solution 1 – Use antivirus specific removal tools

Completely uninstall your old antivirus programs using these antivirus removal tools.  Download and run the tool available for the antivirus you used before installing Windows Defender.

Then restart your computer and Windows Defender should be able to install the latest updates.

In addition to antivirus removal tools, you can also use uninstaller applications to remove your antivirus. If you’re not familiar, uninstaller applications are specially designed to uninstall any program and remove all its files and registry entries from your PC.

By using one of these tools, you’ll completely remove any application from your PC along with any leftover files. As a result, you will prevent any leftover files from interfering with Windows Defender.

There are many great uninstaller applications, and if you’re looking for one, feel free to try IOBit Uninstaller or Revo Uninstaller.

All these applications are rather simple to use, and using them you should be able to remove your third-party antivirus and its leftover files with ease.

Solution 2 – Clean boot your computer

Third-party applications can sometimes interfere with Windows Defender and cause An unexpected problem occurred error message to appear.

This can be caused by third-party startup applications, and in order to fix this issue, you need to perform a Clean boot. This is rather simple and you can do it by following these steps:

  1. Press Windows Key + R and enter msconfig. Now press Enter or click OK.
    Windows Defender unexpected error sorry we ran into a problem
  2. System Configuration window will now appear. Go to Services tab and check Hide all Microsoft services. Now click Disable all button.
    Windows Defender unexpected error sorry we ran into a problem
  3. Now go to Startup tab and click Open Task Manager.
    Windows Defender security center not working
  4. Once the Task Manager opens, you’ll see a list of startup applications. Right-click the first entry on the list and choose Disable from the menu. Repeat this step for all startup applications on the list.
    Windows Defender unexpected error please try again
  5. After you disable all startup applications, close Task Manager and go back to System Configuration window. Click Apply and OK and restart your PC.
    Windows Defender keeps stopping

Once your PC restarts, check if the problem still persists. If not, it means that one of the disabled apps or services was causing it. If you want to find out which app is the problem, disable apps and services one by one or in groups, save changes and restart your PC.

Keep in mind that you’ll have to repeat this several times. Once you find the problematic application, you can disable it or remove it from your PC.

Solution 3 – Check your system files

The System File Checker tool repairs corruption in system files. Use this tool to verify whether Windows Defender is corrupted or not, which could explain why you receive the An unexpected problem occurred error message.

To perform an SFC scan, you just need to do the following:

  1. Press Windows Key + X to open Win + X menu and choose Command Prompt (Admin) or PowerShell (Admin) from the menu.
    Windows Defender unexpected error sorry we ran into a problem
  2. Type the command sfc /scannow > hit ENTER > wait for the scan to complete.
    Windows Defender keeps stopping

If SFC scan doesn’t solve the problem, or if you can’t run SFC scan at all, you might be able to fix the issue by using DISM scan instead. To do that, just do the following:

  1. Start Command Prompt as administrator.
  2. When Command Prompt starts, enter DISM /Online /Cleanup-Image /RestoreHealth and press Enter to run it. DISM scan will now start. Keep in mind that DISM scan can take up to 30 minutes, so don’t interrupt it.
    Windows Defender security center not working

Once the DISM scan is finished, check if the problem still persists. If the issue is still present, or if you couldn’t run SFC scan before, be sure to repeat SFC scan once again and check if that fixes the problem.

Solution 4 – Restart the Security Center Service

According to users, sometimes certain services can cause An unexpected problem occurred error to appear. However, this is just a temporary problem and you can fix it simply by resetting the problematic service. To do that, you just need to follow these steps:

  1. Press Windows key + R > launch Run.
  2. Type services.msc > hit Enter.
    Windows Defender security center not working
  3. In Services, search for Security Center.
  4. Right-click on Security Center > click on Restart.
    Windows Defender unexpected error please try again

In addition to the Security Center service, some users are also recommending to reset Windows Defender Service, so be sure to do that as well. After resetting the required services, check if the problem still persists.

Solution 5 – Make sure that your Windows is up to date

Windows Defender is a core component of Windows 10, and if you’re getting An unexpected problem occurred error message, you might be able to fix the problem simply by updating your Windows. By default, Windows 10 will automatically install the missing updates, but sometimes you might miss an update due to certain bugs.

However, you can always check for updates manually by doing the following:

  1. Press Windows Key + I to open the Settings app.
  2. Now go to Update & Security section.
  3. Click Check for updates button in the right pane.

Windows will now check for available updates and download them in the background. Once the updates are downloaded, they will be installed automatically as soon as you restart your PC.

Keeping your PC up to date is important, and if you’re having problems with Windows Defender, be sure to update Windows and check if that solves the issue.

Solution 6 – Make changes to your registry

According to users, if Windows Defender is giving you An unexpected problem occurred error, you might be able to fix it simply by changing your registry. To do that, you just need to follow these simple steps:

  1. Press Windows Key + R and enter regedit. Now press Enter or click OK.
    Windows Defender unexpected error please try again
  2. When Registry Editor opens, in the left pane navigate to HKEY_LOCAL_MACHINESOFTWAREPoliciesMicrosoftWindows Defender. In the right pane, double-click DisableAntiSpyware DWORD. If this value isn’t available, you’ll need to create it by right-clicking the empty space and choosing New > DWORD (32-bit) Value.
    Windows Defender keeps stopping
  3. Set the Value data to 0 and click on OK to save changes.
    Windows Defender unexpected error sorry we ran into a problem

After doing that, the problem with Windows Defender should be resolved and you should be able to use it without any problems.

An unexpected problem occurred error can prevent you from running Windows Defender, but as you can see, this issue can be easily resolved.

Not being able to use Windows Defender can be a security risk, but we hope that you managed to solve this problem using one of our solutions.

FAQ: Read more about Windows Defender

  • Why Windows Defender is not working?
There can be a lot of issues causing this problem but the most encountered and dangerous culprits are virus and malware. Once you get infected, their first mission is to disable any type of protection you installed on your computer. So the first step would be to perform a virus scan and use specific antivirus and malware removal tools.
  • Why can’t I turn off Windows Defender?
First, it’s not recommended to turn off Windows Defender Antivirus. However, to do that click Start, search for Windows Security and click it to start. Next, click on Virus & threat protection and click the Manage settings in the Virus & threat protection settings section. The last step is to toggle OFF the Real-time protection switch.
  • How do I reinstall Windows Defender?

You probably disabled it or turned it off, not uninstalled it. To enable it again, press the Windows button and then search for Windows Defender. Click on it to start, then manage the settings in the Virus & threat protection settings section and turn ON the Real-time protection switch.

  • Editor’s Note: This post was originally published in May 2018 and has been since revamped and updated in March 2020 for freshness, accuracy, and comprehensiveness.
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