Effective ways to troubleshoot fatal system error “C000021a”

Error messages are common and each one of them is capable of disrupting the smooth functioning of your computer irrespective of its brand and make. Usually, these errors can make your system useless and you are left clueless about the next step that can help you out of this crisis. One such error message is “STOP: c000021a Fatal System Error,” which is popularly known as Blue Screen of Death (BSoD). BSoD is caused due to various reasons and it terminates the Windows logon process. The system shuts down suddenly causing you to lose all unsaved work. While your system gets this error the screen turns blue suddenly showing you the error message.

This article will let you know about the causes and the possible resolutions, so that you can understand the problem better and fix it without any external tech assistance.

Causes of the C000021a error

This error can occur due to either of the Winlogon.exe or Csrss.exe files not working due to any reason. After the Windows NT kernel finds these files not working it causes the system to stop and then it flashes the “STOP: c000021a {Fatal System Error}” with a blue screen. Moreover, the error can also be caused due to the following reasons:

  • Installation of inappropriate and mismatched system files
  • Failure of service pack installation
  • Faulty restoration of file by a backup program
  • Installation of an incompatible third party program
  • Installation of incompatible Windows update
  • Problem with RAM.

Ways to fix the C000021a error

Here are some of the ways by which this error can be rectified:

Removal of third-party GINA DLL files

In most of the cases this error occurs due to changes made to the Windows GINA DLL (Msgina.dll) files by a third party software. To resolve this error you need to follow the below mentioned steps:

  • Start the process by beginning a hunt for the third-party GINA DLL files
  • In the registry editor navigate to the following registry key


  • Now delete the “ínstcat” file and restart the computer.

Removal of newly installed software

The error may occur in case of any new installation of:

  • Updated device driver
  • System service
  • Third party software.

In such a scenario the ideal solution is to remove or disable the newly installed software.

Removal of incompatible software

As discussed above, the C000021a error may also occur due to incompatible software or application. While looking for resolutions to fix this error you must remove the incompatible software by using the Recovery Console. This you can do by navigating the below mentioned path.

“Start” menu >> Control Panel >> Add or remove programs.

Here you need to select the program that you find incompatible with the system and finally click on “Remove” button.

Restore the system to the last known good configuration

This is another way of resolving the C000021a error. This would take the system to the previous stage when all its components were working fine. Just follow the below mentioned guidelines to perform it.

  • Begin the process by clicking on “Start” and then on “Shut down”
  • Now click on “Restart” and then “OK”
  • Press “F8” when you see the message allowing you to launch the Window in “Safe Mode”
  • Now you can choose the option “Last known configuration” with the help of arrow keys on your keyboard
  • Finally press “Enter.”

This will help you to take the system to the last known configuration and get rid of problems that may be caused due to the installation of an inappropriate driver, corrupt or missing driver files or corrupt registry keys. Your system gets restored to the closest previous stage when it was working fine and thus you can fix the C000021a error conveniently.

Although, the tips mentioned above are really very useful to tackle this error but issues may occur if the steps are not applied sequentially and in the right manner. If you are unable to perform these technical steps or are running short of time to do these, then the best way is to call an experienced computer support service provider.


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Effective ways to troubleshoot fatal system error “C000021a”
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