Fix: Windows Defender won’t turn on

2 minute read

Many Windows 10 users are reporting they can’t turn on Windows Defender because Microsoft’s antimalware tool detects there is another antivirus software running, although users confirm they have uninstalled all third-party security software.

This not the first time users have reported they cant’ turn on Windows Defender, but we can’t help but notice there has been an explosion of issues surrounding Windows 10’s built-in antivirus following the Anniversary Update release.

Users are complaining they can’t turn on Windows Defender

I can not turn on windows defender. The message from Microsoft said to uninstalled 2 antivirus programs that were installed. I did this, restarted PC. Still can not turn it on, and is still saying you are running another antivirus software. The are both uninstalled.

It says “Limited periodic scanning is on”. I don’t want this I want – Windows Defender “Real Time Protection”

If you even encounter such errors while trying to turn on Windows Defender, follow the workarounds listed below.

Fix: Windows Defender won’t turn on

Solution 1 – use antivirus specific removal tools

When you uninstall third-party antivirus solutions using the Uninstall option from the Control Panel, it’s possible that some files remain undetected and this prevents you from running Windows Defender. Check out this list of antivirus removal tools, and run the tool available for the antivirus you used before installing Windows Defender.

Uninstall the remnants of your previous antivirus, restart your computer and Windows Defender should be automatically enabled.

Solution 2- 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.

  1. Type cmd in the search box > right-click Command Prompt > Run as administrator.
  2. Type the command sfc /scannow > hit ENTER > wait for the scan to complete.

Solution 3 – clean boot your computer

  1. Type System Configuration in the search box > hit Enter
  2. On the Services tab >  select the Hide all Microsoft services check box > click Disable all.

hide all microsoft services windows 10

3. On the Startup tab > click on Open Task Manager.

4. On the Startup tab in Task Manager > select all items > click Disable.

disable start up items windows 10

5. Close the Task Manager.

6. On the Startup tab of the System Configuration dialog box >click OKrestart your computer.

Solution 4 – Restart the Security Center Service

  1. Press Windows key + R > launch Run.
  2. Type services.msc > hit enter.
  3. In Services, search for Security Center.
  4. Right click on Security Center > click on Restart.

security center windows 10

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