Once a program that scanned for and removed only spyware from your PC, Windows Defender has evolved into a full-fledged antivirus tool on newer versions of the operating system. While it does a respectable job of guarding your system against viruses, malware and other unwanted pests, Microsoft's integrated option isn't everyone's protection method of choice.
If you're interested in installing a different program to protect your PC, you may first want to disable Windows Defender. If you're just looking to temporarily turn off Defender for troubleshooting purposes, that can be done as well by following the instructions below.