Even if Windows Defender is offered for free and it has decent protection features, some people might prefer other applications to secure their system from spyware and other threats. In this case there is no point in having two similar applications running at the same time, both of them consuming system resources. This is why disabling Windows Defender can be a good idea.
Windows Defender hasn’t changed much over the years. In Windows 10 you can turn it off by first opening it. Click the search icon (magnifying glass) in the bottom-left corner of the screen, type “Windows Defender” and open it. Now click the “Settings” button and there you can manage it.
This is how you disable Windows Defender in Windows Vista, 7 and Windows 8:
Launch Windows Defender and go to Tools -> Options.
Here you will find a lot of configuration options. Scroll down to the end of the list. You will find there a section called Administrator options. Deselect the Use Windows Defender box and press the Save button.
If UAC is turned on, you will need to confirm that you want to continue with the change.
Now you will receive a notification saying that “Windows Defender is turned off”. Click on Close and you are done.