How to Fix Blue Screen of Death Stop Error c000021a

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.


Step 1 – Error c000021a

This blue screen of death stop error c000021a will be displayed when your system is in normal booting process. When the windows logo screen will appear, you will suddenly see the c000021a Fatal System Error.

When will erorr c000021a be displayed?

Step 2 – Last Known Good Configuration

As a result, the Advanced Boot Options screen will appear. From there, select the option titled “Last Known Good Configuration” and hit the enter key.
With the help of this option, Windows will bypass the corrupt startup files which are causing the fatal error in your system and will boot your system in the normal condition. Once the reboot has completed, your desktop will appear and that’s it. You have successfully resolved the blue screen of death stop error c000021a.

Resolve error c000021a