How to Fix Windows Stop Code: 0xc000021a?

What Is Error 0xC000021a on Windows 10?

Error 0xC000021A is one of diverse critical Blue Screen of Death (BSOD) error that occurs when Windows detects a fatal system-level failure. Unlike common application crashes, this stop code indicates that an essential system process—such as Winlogon.exe or Csrss.exe—has unexpectedly terminated or failed to run correctly.

When this error appears, Windows immediately shuts down to prevent further damage. As a result, the system often becomes unbootable, repeatedly restarting or getting stuck on a blue error screen. This makes Error 0xC000021A particularly disruptive, as users cannot access the desktop or troubleshoot from within Windows.

Why It Occurs on Windows Startup?

Error 0xC000021a most commonly appears during the Windows startup process, when the operating system is loading core services and system files. At this stage, Windows relies heavily on system integrity, so even minor inconsistencies can trigger a critical failure.The most common causes include:

⭕Corrupted system files

Sudden power loss, disk errors, or malware can damage critical Windows files, causing essential processes to fail at startup.

⭕Failed or incomplete Windows updates

Interrupted updates may replace or modify system components incorrectly, leading to compatibility issues during boot.

⭕Incompatible drivers or third-party software

Low-level drivers, security software, or system utilities that conflict with Windows can prevent system processes from launching.

⭕File system error or disk errors

Bad sectors or logical file system corruption on the system drive can stop Windows from reading required files.

How to Fix Windows Stop Code: 0xc000021a?

When dealing with Error 0xC000021a, it is always a good idea to follow a logical repair sequence—beginning with non-destructive methods and only moving to advanced solutions if necessary.

Method 1: Run Startup Repair

First of all, we need to enter Windows Recovery Environment (WinRE) where you can find several Windows boot repair tools or options to repair some common boot issues without loading the full operating system, making it the safest place to begin troubleshooting.

In many cases, Windows automatically enters Recovery Mode after repeated failed boots. If it doesn’t, you can force it by interrupting startup several times. Once in WinRE, select: "Troubleshoot → Advanced options".

In the "Advanced Options" screen, you can select "Startup Repair".

Startup Repair is designed to automatically detect and fix boot-related issues.

Method 2. Repair Corrupted System Files

If the Startup Repair failed to fix the stop code:0xc000021a with the message: "Automatic Repair couldn't repair your PC", you can check whether critical system files are corrupted. Windows provides built-in tools—SFC and DISM—to scan and repair system components that may prevent Windows from booting correctly.

First, boot your computer into WinRE environment, choose "Command Prompt" from the Advanced Options window.

Once the Command Prompt opens, type the following command and press Enter: sfc /scannow

The System File Checker will scan all protected system files and automatically replace corrupted ones. If SFC reports errors that it cannot fix, you should continue with the DISM command, which repairs the Windows image itself.

If Windows can boot into Safe Mode, run:

DISM /Online /Cleanup-Image /RestoreHealth

If the system cannot boot normally and you are working from the recovery environment, use:

dism /image:C:\ /cleanup-image /revertpendingactions

After the process completes, restart your computer and check whether the stop code has been resolved.

Method 3: Repair Boot Configuration Data (BCD)

If repairing system files does not fix the issue, the problem may lie in corrupted or missing Boot Configuration Data (BCD). BCD controls how Windows starts, and any damage to it can trigger startup-related stop codes like 0xC000021a.

In the Command Prompt window, run the following commands one by one, pressing Enter after each:

bootrec /fixmbr

bootrec /fixboot

bootrec /scanos

bootrec /rebuildbcd

These commands rebuild the master boot record and restore boot configuration data required for Windows startup. Once completed, restart your PC and see if Windows loads normally.

Method 4: Uninstall Problematic Updates or Drivers

If the error code began immediately after a Windows update or driver installation, removing the problematic component may restore system stability.

Step 1. In WinRE, select: "Advanced options → Uninstall Updates"

Step 2. You will be presented with two options: "Uninstall latest quality update" and "Uninstall latest feature update".

Step 3. Start by uninstalling the latest quality update, as it is the most common cause of startup-related errors. Choose your target operating system, confirm your selection and allow Windows to remove the update.

If the issue persists after rebooting, repeat the same steps and uninstall the latest feature update, which is a larger system upgrade and more likely to affect core system components.

Method 5: Perform a System Restore

If uninstalling recent updates or drivers does not resolve the issue, System Restore offers a broader rollback option by returning Windows to a previously stable configuration. This method is especially useful when Error 0xC000021a was triggered by system updates, driver changes, or software installations that are difficult to identify individually.

Step 1. In the Windows Recovery Environment, go to "Advanced options → System Restore".

Step 2. Choose a restore point created before the error occurred.

Windows will restore system files, drivers, and registry settings to that earlier state.Itdoes not affect personal files, but it removes recently installed drivers and updates that may be causing conflicts.

Method 6: Reset or Reinstall Windows (Last Resort)

If none of the above methods resolve Error 0xC000021A, the system may be severely damaged.

At this stage, you can choose to:

• Reset this PC (Keep my files) to reinstall Windows while preserving personal data

• Perform a clean installationvia USB installation media if system corruption is extensive

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FAQs about the Stop Code

Can RAM Cause a 0xC000021a Error?

Yes. Faulty or incompatible RAM can cause memory access violations, leading to system process crashes during startup. If critical processes like Winlogon.exe fail due to memory errors, Windows may trigger the 0xC000021A stop code. Running Windows Memory Diagnostic or testing RAM modules individually can help identify this issue.

Can a Virus Cause a 0xC000021a Error?

Yes. Malware can corrupt or replace critical system files and interfere with essential Windows processes. Certain viruses target boot-related components, which may result in startup failures and trigger the 0xC000021a BSOD. Performing an offline malware scan from Windows Recovery Environment or using trusted antivirus rescue media is recommended.

Can disk Errors Trigger the 0xC000021a Stop Code?

Yes. File system corruption or bad sectors on the system drive can prevent Windows from reading essential system files during boot. When critical data becomes inaccessible, Windows may terminate core processes and display the 0xC000021A error. Running CHKDSK from Command Prompt in Recovery Mode can help detect and repair disk-related issues.

Is Error 0xC000021a Related to Driver Incompatibility?

Yes. Incompatible, outdated, or corrupted drivers—especially low-level drivers such as graphics, storage, or security drivers—can cause system-level conflicts. If a driver interferes with protected Windows processes, the system may shut down with a 0xC000021a stop code. Rolling back or uninstalling recently added drivers often resolves the problem.

Will reinstalling Windows always fix 0xC000021a?

Reinstalling Windows usually resolves the error because it replaces corrupted system files and resets configurations. However, if the underlying cause is faulty hardware (such as RAM or a failing disk), the error may reappear even after reinstallation. Hardware diagnostics should be performed if the issue persists after a clean install.

Conclude

The "Windows stop code 0xC000021a"is a serious startup error that usually indicates corruption in critical system files, boot configuration issues, or hardware-related conflicts. As this guide shows, there are still several methods to help troubleshoot this problem.

Sincethis error often leaves Windows "unbootable", protecting your data should always be a priority. If standard backup methods are unavailable, professional recovery solutions such as MyRecover can help retrieve important files from a crashed or inaccessible system without requiring prior backups.

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