How to Fix STOP: C000021A (0xC000026C / 0xC000034) Blue Screen Error in Windows XP

🧩 Introduction

If your Windows XP computer suddenly crashes and displays a STOP: C000021A {Fatal System Error} with a status code like 0xC000026C or 0xC000034, don’t panic.

This is a common Blue Screen of Death (BSOD) error caused by corrupted system files, incompatible drivers, or failed updates.

In this guide, you’ll learn what the STOP: C000021A error means, what causes it, and step-by-step methods to repair your system and get Windows XP running again.

⚙️ What Is the STOP: C000021A Error?

The STOP: C000021A error (also known as a Fatal System Error) occurs when the Windows Logon Process or Client Server Runtime Subsystem (CSRSS.exe) fails.

When these critical components stop working, Windows XP forces a system halt to prevent further damage.

You might see one of these messages:

STOP: C000021A {Fatal System Error}
The Windows Logon Process system process terminated unexpectedly with a status of 0xC000026C (0x00000000 0x00000000)

or

STOP: C000021A {Fatal System Error}
The Windows SubSystem system process terminated unexpectedly with a status of 0xC000034 (0x00000000 0x00000000)

💡 Common Causes of STOP: C000021A (0xC000026C / 0xC000034)

• Corrupted or missing system files such as winlogon.exe or csrss.exe
• Incomplete Windows updates or driver installations
• Damaged hard drive sectors or file system errors
• Virus or malware infections
• Improper shutdowns or power interruptions
• Third-party software conflicting with Windows system processes

🧰 Before You Begin

Before attempting repairs, make sure you have:

• A Windows XP installation CD or bootable USB
• Access to the Recovery Console
• Basic knowledge of command line operations
• A backup of important data if possible

🪛 Step-by-Step Guide to Fix the STOP: C000021A Error

🪜 Step 1: Boot into the Recovery Console

1. Insert your Windows XP CD and restart the computer.
2. When prompted, press any key to boot from CD.
3. At the setup screen, press R to access the Recovery Console.
4. Choose your Windows installation (usually 1) and enter the administrator password.

🧩 Step 2: Run CHKDSK to Repair Disk Errors

In the command prompt, type:

chkdsk /r

Press Enter and allow Windows to scan and fix disk issues.
Once complete, type exit to restart your computer.

🧰 Step 3: Replace Corrupted System Files

If the error persists, boot again into the Recovery Console and type:

cd C:\Windows\System32
copy C:\Windows\System32\DllCache\winlogon.exe C:\Windows\System32\
copy C:\Windows\System32\DllCache\csrss.exe C:\Windows\System32\

Press Y to confirm file replacement.

⚙️ Step 4: Try “Last Known Good Configuration”

1. Restart the computer.
2. Continuously press F8 during boot.
3. Select Last Known Good Configuration and hit Enter.

This reverts your system to the most recent settings that worked correctly.

🔄 Step 5: Remove Recently Installed Software or Drivers

If you recently installed a program or driver before the crash, uninstall it in Safe Mode:

1. Press F8 during boot and select Safe Mode.
2. Open Control Panel → Add or Remove Programs.
3. Remove any suspicious or recent installations.

💽 Step 6: Perform a Repair Installation (Last Resort)

If none of the steps above work:

1. Boot from the Windows XP CD.
2. Choose Install Windows XP, then Repair when prompted.
3. This reinstalls system files while keeping your data intact.

🧠 When to Suspect Hardware Problems

If you continue to get the STOP: C000021A error after reinstalling or repairing Windows XP, the issue could be hardware-related.
Common culprits include:

• Failing hard drives
• Defective RAM modules
• Overheating or unstable power supply units (PSU)

Use tools like MemTest86 or manufacturer diagnostic software to test your hardware.

🔗 References and Helpful Links

• Microsoft Support – Troubleshooting STOP: 0xC000021A Errors
• How to Use the Recovery Console in Windows XP

🕓 Updated: October 2025

Although Windows XP is an older operating system, many legacy systems still depend on it.

This updated guide ensures you have reliable, working solutions for one of XP’s most infamous blue screen errors.