Microsoft Windows Error Code 0xC0000077: How to Fix It

Medium 30-60 minutes Medium Severity Verified June 2026
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Error Code
0xC0000077
Brand
Microsoft Windows
Product Type
operating_system
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
30-60 minutes
Error 0xC0000077 indicates that Windows encountered an Access Control List (ACL) that is malformed or corrupted, preventing certain system or application files from being accessed. This often occurs due to file system corruption, a failed update, or a faulty software installation. The following steps will help you resolve the issue.
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Tools You'll Need

How to Fix Error Code 0xC0000077

  1. Run System File Checker (SFC)

  2. Run DISM to Repair System Image

  3. Perform a Startup Repair

    Back up important data before performing startup repair if you suspect data loss.

  4. Check Disk for File System Errors

    Do not interrupt the disk check process as it may cause data loss.

  5. Reset Windows Security Settings (ACL) Using icacls

    This command resets permissions for all files in the current directory. Use with caution and ensure you are in the correct directory (e.g., C:\Windows\System32).
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When to Call a Professional

If none of the above steps resolve the error, consider contacting a professional technician or Microsoft Support, especially if you suspect hardware failure or extensive system corruption. A clean reinstall of Windows may be necessary.

Frequently Asked Questions

What does error code 0xC0000077 mean?
It means Windows encountered a malformed or invalid Access Control List (ACL), which prevents proper access to files or system components.
Can I fix error 0xC0000077 without reinstalling Windows?
Yes, often you can fix it by running SFC, DISM, or a startup repair. A reinstall is a last resort.
Is error 0xC0000077 caused by malware?
While malware can corrupt ACLs, the error is more commonly due to file system corruption or failed updates. Running a full antivirus scan is still recommended.
Will I lose data when fixing error 0xC0000077?
Most repair steps (SFC, DISM, chkdsk) do not delete personal files. However, if you need to reinstall Windows, back up data first.
How do I create a Windows installation media for startup repair?
Use Microsoft's Media Creation Tool to download and create a bootable USB or DVD from another working PC.

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