Microsoft Windows Error Code 0xC000021D: How to Fix It

Medium 30-60 minutes Medium Severity Verified June 2026
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Error Code
0xC000021D
Brand
Microsoft Windows
Product Type
operating_system
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
30-60 minutes
Windows error code 0xC000021D indicates a hard error in the 16-bit subsystem (Virtual DOS Machine). This usually occurs when system files are corrupted or a driver is incompatible, often after a failed update or software installation. Follow these steps to diagnose and resolve the issue.
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Tools You'll Need

How to Fix Error Code 0xC000021D

  1. Boot into Safe Mode

  2. Run System File Checker (SFC)

    Do not close the Command Prompt until the scan is finished.

  3. Run DISM Tool

    This process can take up to 30 minutes. Ensure your internet connection is stable.

  4. Check for Recent Changes

  5. Perform System Restore

    System Restore will not affect your personal files but may remove recently installed programs.

  6. Repair Windows Using Installation Media

    Ensure you have backed up important data before proceeding with major repairs.
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When to Call a Professional

If none of the above steps work, the error may indicate a failing hard drive or deeper hardware issues. Consider contacting a professional technician to diagnose hardware components.

Frequently Asked Questions

What causes Windows error 0xC000021D?
This error is typically caused by corrupted system files, a failed driver installation, or a damaged Windows update. It can also occur if the 16-bit subsystem files (like ntvdm.exe) are missing or damaged.
Can I fix error 0xC000021D without losing data?
Yes, most fixes like SFC, DISM, and System Restore do not delete personal files. However, it's always recommended to back up your data before performing repairs.
Does error 0xC000021D mean my computer is broken?
No, it's a software error, not hardware failure. It can usually be resolved with the steps above. If you suspect hardware issues, run a memory or disk diagnostic.
How do I boot into Safe Mode if I can't access Windows?
Turn on your PC and press F8 repeatedly until the Advanced Boot Options menu appears. Alternatively, interrupt the boot process three times (forced shutdown) to trigger automatic repair, then navigate to Troubleshoot > Advanced Options > Startup Settings > Restart > Safe Mode.
Is error 0xC000021D the same as a Blue Screen of Death?
Yes, this error often results in a BSOD (Blue Screen of Death). The steps above can help resolve the underlying cause.

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