Error 0xc000021a in windows 10/11 or any previous Windows operating system is also called as stop error or blue screen error. There are several scenarios your computer may get this error 0xc000021a. Scenario -1: When your computer running any old version of Windows operating systems like Windows 8 or Windows 7 and you are trying to upgrade to window 10. Next Scenario -2: When you update any software package from pending updates.