In this tutorial, we will teach you how to fix blue screen of death stop error c000021a.
The error “c000021a” occurs when the user-mode subsystem has been compromised and its security is in question. The user-mode subsystem refers to the Client Server Run-Time Subsystem (CSRSS) or WinLogon. Then the security is under question, the operating system operates in kernel mode. Windows cannot run properly without WinLogon or CSRSS.