The “Security and Maintenance” Control Panel applet may warn you that Windows Defender is disabled and no anti-virus is protecting your system. If you open Windows Defender interface, it offers to Turn On protection, but the button doesn’t work.
In the Services MMC, when you try to start Windows Defender Antivirus Service or Windows Defender Antivirus Network Inspection Service, you may get
Error 577, as seen below:
Sometimes, you may see a different error.
Fix: Windows Defender Error 577 – Service fails to start
This problem can happen if you’ve been using a 3rd party anti-virus solution and later uninstalled it or its trial period has ended. Installation of a third-party anti-virus program automatically disables Windows Defender anti-virus. If a trial version of your anti-virus software (i.e. Avast, McAfee, Norton, etc) came preinstalled on your computer (or you installed one), it most likely turned Windows Defender off to avoid conflicts.
(Related article: Fix: Malwarebytes Disables Windows Defender or 3rd Party Anti-Virus)
Until the third-party anti-virus software has been completely uninstalled, Windows Defender will remain disabled. Sometimes, you’ll need to download and run the anti-virus software vendor’s uninstaller/cleanup tool to remove traces of the software completely. Once done, Windows Defender and the related services should resume automatically.
Step 1: Uninstall third-party anti-virus software
Open Apps & Features or Programs and Features and uninstall the third-party software. If the uninstall process fails, or the uninstall doesn’t fix the problem even after restarting the system, use the specialized cleanup tool from the respective anti-virus software vendor.
- Avast Uninstall Utility (aswClear)
- AVG Remover
- Avira: Manual uninstallation instructions
- Bitdefender Uninstall Tools
- Removal tool for Kaspersky products (kavremover)
- F-Secure Uninstall Tool
- Remove McAfee products
- Uninstall ESET manually using the ESET uninstaller tool
Also, see the comprehensive list of anti-virus uninstaller tools compiled by ESET Knowledgebase team: Uninstallers (removal tools) for common Windows antivirus software.
Step 2: Fix Windows Defender Registry Settings
If clean uninstalling third-party anti-virus solution and restarting Windows doesn’t help, follow these steps in addition:
- Download PsExec from Microsoft’s Windows Sysinternals site. Unzip and extract the tool to a permanent folder, say d:\tools
- Open an elevated or admin Command Prompt window.
- Type the following command, and press ENTER:
- In the Registry Editor window, go to the following key:
DisableAntiVirusand sets its data to
DisableAntiSpywareand sets its data to
- Go to the following policies branch:
- Delete the two values
DisableAntiSpywareif found in the above location.
- Exit the Registry Editor.
- Restart Windows and see if Windows Defender is able to start correctly.
d:\tools\psexec.exe -sid c:\windows\regedit.exe
PsExec command-line starts the Registry Editor under
LOCALSYSTEM account so that you can modify protected areas in the registry.
Automate the above steps using REG file
You can automate the steps
4-8 above by importing the REG file in the Registry Editor (launched using
PsExec tool). Download fix-defender-error-577.zip, unzip and extract the REG file to desktop. In the Registry Editor window, click the File menu, click Import… and select the file
fix-defender-error-577.reg to apply it. Exit the Registry Editor and restart Windows.
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About the author
Ramesh Srinivasan founded Winhelponline.com back in 2005. He is passionate about Microsoft technologies and he has been a Microsoft Most Valuable Professional (MVP) for 10 consecutive years from 2003 to 2012.