This option is named “limited periodic scanning”. You can also manually perform scans of your entire system or specific folders. But a new option allows Windows Defender to provide some help without providing full real-time protection. As such, Windows Defender normally disables itself if you install another antivirus, getting out of the way. Generally, you aren’t supposed to run two always-on antivirus programs at once. Windows 10 comes with Windows Defender, a built-in antivirus tool to help protect your PC from malware. With the Anniversary Update, Windows Defender can keep protecting your PC by providing a second layer of protection, even if you install another antivirus.