System file and kernel errors

REGISTRY_ERROR (0x00000051)

Stop code 0x00000051, also written 0x51. Here is what it means, what usually causes it, and the safest order to work through fixes on Windows 11 and Windows 10.

In short

Windows hit a severe problem reading or maintaining the registry. Storage trouble or file-system damage is the first thing to rule out.

What REGISTRY_ERROR means

Bug check 0x51 means a severe registry error occurred. Microsoft describes two causes: an I/O error while the registry was reading one of its files, which can come from hardware problems or file system corruption, and a failed refresh operation that only the security system uses and that fails only when resource limits are reached. In practice, the first is the one home users meet, which is why the drive and file system deserve attention before anything else.

Common causes

A drive that is failing or returning read errors
File system corruption, often after power loss or a forced shutdown
A loose or faulty storage cable, or an unreliable storage controller
Registry files damaged during an interrupted Windows update

How to fix REGISTRY_ERROR

Work through these in order and test after each one. Stopping as soon as the crashes stop tells you which change mattered.

Back up your files first. If Windows still starts, copy important files to another drive before running any repair. Read errors on the drive that holds the registry can get worse under heavy repair activity.
Check the health of the drive. Read the SMART data with the drive maker's tool or CrystalDiskInfo and look for reallocated or pending sectors, media errors and a low remaining-life figure. Back up important files first if the drive reports any warning.
Scan the file system. Open Terminal (Admin) and run chkdsk C: /scan, which checks the volume without locking it for repair. If it reports problems, follow its guidance, ideally after your backup is complete.
Repair Windows system files. Open Terminal (Admin) and run sfc /scannow. If it reports damage it could not repair, run DISM /Online /Cleanup-Image /RestoreHealth, restart, and run sfc /scannow once more.
Start in Safe Mode if Windows will not load. Hold Shift while choosing Restart, or let Windows fail to start three times to open the recovery menu. Choose Troubleshoot, Advanced options, Startup Settings, Restart, then Safe Mode. If Windows is stable there, a driver or startup program is the likely cause.

Reading the crash evidence for 0x51

Microsoft’s reference lists the third parameter as a pointer to the registry hive and the fourth as the result of its hive check, when available. These are meant for debugging, so most people will get more from Event Viewer: look in Windows Logs, System for disk, ntfs or Kernel-Power entries near the time of each crash.

Because the registry lives in files on disk, the cause is usually found outside the registry itself. A drive health tool and the Event Viewer disk entries are the quickest ways to tell storage trouble from a one-off interruption.

Match what you observe to the next check
What you observe	What it may suggest	Next check
Disk or ntfs errors appear in Event Viewer near the crash	The registry could not read its files reliably	Check drive health and run `chkdsk C: /scan` after backing up
The crash followed a power cut or forced shutdown	File system damage from an unclean shutdown	Run the file system scan and System File Checker
The crash followed an interrupted Windows update	Registry or system files may be inconsistent	Run DISM and System File Checker, then retry the update
Other stop codes appear on the same PC	Storage or memory may be unreliable more broadly	List every code from Event Viewer and test both drive and memory

Source: Microsoft Learn: Bug Check 0x51 REGISTRY_ERROR ↗

When to stop and protect your data

If the drive reports bad or pending sectors, or REGISTRY_ERROR returns after a repair, treat the drive as unreliable: back up what you can and plan to replace it rather than reinstalling onto the same disk.

Not sure this is your code?

The stop code appears as text on the blue screen. If the PC restarted before you could read it, open Event Viewer, then Windows Logs, then System, and look for a BugCheck event with ID 1001. You can also search all stop codes.

Related guides

Other system file and kernel errors

Frequently asked questions

What does REGISTRY_ERROR mean?

Windows hit a severe problem reading or maintaining the registry. Storage trouble or file-system damage is the first thing to rule out. Bug check 0x51 means a severe registry error occurred. Microsoft describes two causes: an I/O error while the registry was reading one of its files, which can come from hardware problems or file system corruption, and a failed refresh operation that only the security system uses and that fails only when resource limits are reached. In practice, the first is the one home users meet, which is why the drive and file system deserve attention before anything else.

What usually causes REGISTRY_ERROR?

Typical causes: A drive that is failing or returning read errors; File system corruption, often after power loss or a forced shutdown; A loose or faulty storage cable, or an unreliable storage controller; Registry files damaged during an interrupted Windows update.

How do I fix REGISTRY_ERROR (0x00000051)?

A sensible order is: 1) Back up your files first; 2) Check the health of the drive; 3) Scan the file system; 4) Repair Windows system files. If the drive reports bad or pending sectors, or REGISTRY_ERROR returns after a repair, treat the drive as unreliable: back up what you can and plan to replace it rather than reinstalling onto the same disk.

Is REGISTRY_ERROR caused by a registry cleaner or a bad registry edit?

It can be, but Microsoft’s own description centres on I/O errors reading the registry files, which points to the drive or file system. A related stop code, BAD_SYSTEM_CONFIG_INFO, is the one Microsoft links to missing keys after manual edits.

Do I need to reinstall Windows after REGISTRY_ERROR?

Not as a first step. Back up your files, check the drive and file system, and run System File Checker. Reinstall onto a new drive if the old one is reporting errors.

Use this guidance carefully

A stop code can have several causes, and these steps are general guidance rather than a diagnosis of your PC. If your data matters, back it up before repairs. If the problem continues, a hardware technician can test the parts.

See our testing methodology·Read our editorial policy