Windows Defender is the default Antivirus that comes preloaded in almost all versions of windows. it’s no doubt the most convenient way to defend your computer against malware and virus attacks. However, quite recently a lot of reports have been coming in where users are unable to turn their Windows Defender on and it seems like it has been disabled permanently. An outdated Windows OS may cause the problem of Windows Defender not turning on. Some users reported that they had been able to fix the problem simply by installing the latest Windows update – latest signature updates are necessary for Windows Defender to keep your PC secure.