This article will show how to enable or disable Windows Defender in Windows 10. Windows Defender is the built-in antivirus with any Windows 10 PC.NOTE: Windows Defender will be automatically disabled on your Windows 10 PC if there is another antivirus installed such as ESET, McAfee, Norton and you will be unable to enable Windows Defender.Here is how to enable/disable Windows defender:1. Right click on the Start button, typically found at the lower left corner of the screen, then click on Settings. 2. From the Windows Settings screen that appears, click on Update & Security. 3. From the options on the left, click on Windows Defender. 4. Under Real-time protection, here you can toggle the switch to enable (On) or disable (Off) Windows Defender. Changes will be saved automatically. If the switch is greyed out and unable to be changed, Windows Defender is disabled due to another antivirus program being installed on the computer.