If the button clicked in the previous step was labeled View antivirus options, in the Action Center prompt, click Turn on Windows Defender.If the button clicked in the previous step was labeled View antispyware apps, in the Action Center window, click to highlight Windows Defender and then click the Turn on button.NOTE: The next step will depend on which button you have selected: In the Action Center window, in the Security section, click the View antispyware apps or View anti virus options button.In the System and Security window, click Action Center.In the Control Panel window, click System and Security.NOTES: Because the Control Panel is a traditional Windows Desktop application, if you were not already there, the interface will change to the Desktop and the Control Panel window will open. Press the Windows Logo + X key combination on the keyboard and, from the list, click Control Panel.If you prefer to use Windows Defender to protect your computer, you can disable or uninstall the currently installed anti virus software and then follow the steps below to enable Windows Defender. Microsoft® Windows® Defender is bundled with the Windows® 8 and 8.1 operating systems, but many computers have a trial or full version of other third-party anti virus protection program installed, which disables Windows Defender.

Windows defender not turning on