What is Microsoft defender?
Windows Defender, formerly known as Microsoft AntiSpyware, is a software product that helps combat malware. Windows Defender was initially an antispyware program; it is included with Windows Vista and Windows 7 and is available as a free download for Windows XP and Windows Server 2003. In Windows 8, however, it is upgraded to an antivirus program.
How do I enable it?
First, go to start and in the search bar type in windows defender, next, click on the icon that looks like a chess rook which reads windows defender. You will now get a window pop up which reads windows defender is turned off “click here to turn it on”. Hover your mouse over it and click on it. Your problem is now solved; however, some users may get an error message “The service cannot be started, either because it is disabled or because it has no enabled devices associated with it- Error code (0x80070422)”