Correction of the error "STOP c000021a"

You may encounter this error when you turn on the computer or when you try to restore the system from removable media. After the failure notification window appears, the process is interrupted and it is impossible to continue working with a PC. Next, we will tell you how to deal with this problem and where it comes from.

Methods to fix the error STOP c000021a.

Causes of error

Error STOP c000021a is typical for all modifications of Windows: XP, 7, 8, 10. The following can provoke such:

  1. Violations in the registry entries (see if you changed anything there the day before).
  2. Damage to the hard drive or a temporary failure in his work.
  3. Installing a fresh version of antivirus.
  4. Installing applications that are incompatible with the OS of your modification.
  5. Improper PC shutdown: shutdown during OS upgrade, power outage, etc.

The sudden appearance of a blue screen instead of a standard Windows label can scare any user, however, the error is not fatal at all, contrary to the “Fatal system error” message that appears. It can be fixed in several ways, but this will require a bootable USB flash drive (or disk) with a Windows image in order to gain access to PC control functions.

Fix the error "Fatal system error"

The STOP error code c000021a is resolved in the following ways:

  1. A simple reboot with the choice of “Download last known good configuration” (to do this, when turned on, press F8 several times).
  2. Scanning and restoring important system functions using a special command in the command line.
  3. Restore the system from the boot disk with the addition of whole files from the image and replace them with damaged ones.

With the first point, everything is clear: if you are lucky, the system will roll back to the last successful download by itself, but this happens infrequently. We begin a detailed description of the process of fixing Fatal system error with the second method:

  1. Insert a bootable USB flash drive with Windows and select the last command line option from the menu. Automated recovery options take time away from you, but do not solve the problem.
  2. In the Command line enter: chkdsk c: / r (instead of C, you may have another letter if the system partition has a different name.
  3. Click "Inter" and wait for the completion message.
  4. Next, in the Command line you need to enter: sfc / scannow. This command will launch a full OS check with error detection and correction. Such an event may take more than one hour, periodically, the percentages of the work done will stop for 10-15 minutes - this is normal, it should be so. Do not turn off the computer until the completion message appears.
  5. Now restart the system and make sure that the error has disappeared.

If the Fatal error has not gone away, then here is another option, how to correct the situation:

  1. Boot from the flash drive and go to drive C (it may be called differently).
  2. Find the folder RegBack (using the "Search" will be more convenient, but in general it is located in the config section, which, in turn, is located in System32).
  3. Take out all the elements from it in the config.
  4. And if the RegBack folder is empty, then vice versa, from the config you need to transfer the elements to it: default, sam, security, software, system.
  5. Restart the PC.
  6. Do not be alarmed when you see the Windows welcome message, as if you installed it again - these are not all the settings that we will apply.
  7. Open "Control Panel" - "System and Security" - "Support Center" and select "System Restore".
  8. Remember the day when the computer started up without any problems, and find the corresponding restore point.
  9. Thus, all your presets will return, and you can safely continue to work on the PC.

Also try the following:

  1. Connect the USB flash drive to another PC with a working Windows.
  2. Go to drive C in a folder called Windows, where the System attachment is stored
  3. Copy the following elements to the USB flash drive: Winlogon.exe, Csrss.exe, smss.exe.
  4. Now boot from a flash drive on a damaged PC and transfer the copied files to a similar folder - this way you replace the damaged items with normal ones.


In conclusion, let us say a few words about what to do if a fault with error code c000021a appeared during the launch of the OS from the bootable media:

  1. Check the quality of the boot record: try downloading a disk image from another site or burn it yourself, carefully following the prompts of the program.
  2. Replace disc burning software - some of them often “forget” to include critical files in the distribution.
  3. Check the health of the flash drive / disk. To create a boot record, you need to properly format it - make sure that it is.