How to Fix Cyclic Redundancy Check Error (CRC Error) in Windows?

A Cyclic Redundancy Check error signals data corruption. In many cases, it can be fixed by simple steps like changing cables or running CHKDSK on Windows 10/11. Common causes of CRC error in external hard drives include corrupt files, bad sectors, faulty cables or connections, power loss, and file system corruption. Using tools like CHKDSK, SFC, and ROBOCOPY helps fix many CRC errors on Windows 10/11. Testing your drive on another PC or powered dock can identify if the CRC error stems from hardware or software issues. If DIY fixes fail, professional CRC error data recovery services like Stellar Data Recovery can recover data, even from physically damaged or severely corrupted drives.

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Nothing is more frustrating than copying family photos or backing up official documents on Windows and suddenly seeing the dreaded “Data error (Cyclic Redundancy Check error)” pop up.

Most of the time, the solution to fix the CRC error is as simple as changing a USB cable or re-running the copy command.

However, if the disk has bad sectors or the file system itself is damaged, deeper repairs—or even professional CRC error data recovery—may be needed.

In this guide, we’ll cover every scenario, including steps to fix CRC errors on external hard drives.

First, let’s start with the basics of what a Cyclic Redundancy Check error really means.

What Is a Cyclic Redundancy Check (CRC) Error?

A Cyclic Redundancy Check (CRC) is a mathematical trick that lets a computer confirm that data has not changed between the moment it was saved and the moment it is read back. Think of it as a digital “tamper seal.”

Note: If you are not interested in the technical aspects of Read Error (Cyclic Redundancy Check), you can straightaway jump to the sections on Diagnosing CRC Error and Fixing CRC Error.

How the CRC Math Works

1. Convert the data to binary.

Suppose you save the text “PAY123” to a pen drive. Each character becomes an 8-bit block:

P A Y 1 2 3

01010000 01000001 01011001 00110001 00110010 00110011

2. Append a string of 0s.

The data is extended by adding a number of zero bits at the end. For the common CRC-32 method, this means adding 32 zeros. This padding prepares the data for the division step that follows.

3. Divide by a generator polynomial.

Think of the entire binary string (original data + zeros) as one big number. This number is divided by a special fixed number called the generator polynomial (for CRC-32, it’s 0x04C11DB7). The remainder left after this division is the CRC checksum.

4. Store the remainder.

That remainder is written next to your data on the drive.

5. Verify on read.

When Windows reads the data later, it performs the same division process on the data it received.

If the new remainder matches the stored remainder, it means the data has not changed.	If the remainders don’t match, it means some bits flipped or got corrupted. Windows then stops the operation and returns a Cyclic Redundancy Check error.

Some of the common CRC error messages are:

• “Data error (cyclic redundancy check).”
• “F:\ is not accessible. Data error (cyclic redundancy check).”
• “Cannot initialize disk. Data error (cyclic redundancy check).”
• “File ABC.mp4 could not be copied. Data error (cyclic redundancy check).”
• “CRC check failed”

All such messages point to one thing: Windows reads a checksum that doesn’t tally with the original.

Root Causes: Why Does a Cyclic Redundancy Check (CRC) Error Happen in Windows 10/11?

When you see a CRC error, it means Windows detected that some data didn’t match with the expected value. This can happen for several reasons.

• Bad sectors on your hard disk (HDD) or worn-out blocks on an SSD: Over time, parts of the drive can get damaged or stop working properly.
• Loose, bent, or rusty cables and ports: A poor connection can cause data to be read incorrectly.
• Sudden power loss: If your computer or external drive loses power while downloading or saving data, files might get corrupted.
• Filesystem corruption: Malware or an improper shutdown can scramble NTFS tables, so the stored checksum no longer matches the data.
• Network hiccups: Windows may return Data Error (Cyclic Redundancy Check) if the connection becomes unstable while transferring data over a network.

Typical Situations Where You Might Encounter a CRC Error

Here are some common instances when a CRC error message pops up.

• Plugging in a portable external hard drive: If the drive has been carried around a lot, it might have sustained minor damage, causing a CRC error external hard drive.
• Copying a large file over Wi-Fi: If the connection is unstable, a single lost packet can cause a Data Error Cyclic Redundancy Check and stop the data transfer.
• Running Windows Backup: If the backup destination has bad sectors, the backup will stop with error code 0x80070017.
• Installing Windows from a USB drive: If the USB or the installation files are damaged, checksums won’t match, and the setup will fail.

How to Diagnose Data Error Cyclic Redundancy Check in Windows 10/11?

When you see a Cyclic Redundancy Check error pop up, it means Windows has detected a problem reading your data. Because there are many possible causes—and several DIY fixes—it helps to do a couple of quick checks. These checks give you clues about whether the issue is likely software-related or if the drive itself might be physically damaged.

1. Check the Drive’s Status in Windows

Use the built-in Disk Management tool to see how healthy your drive looks.

• Press Windows key + R, type diskmgmt.msc, and press Enter.
• Find your drive in the list.
• If it says Healthy, that usually means the drive is okay, and the problem might be fixed with software.
• If it says RAW (in the File System column) or Unallocated (in the status column), it means the drive’s file system is damaged—but don’t worry; software fixes can still help.

2. Listen to the Drive

Bring the drive close to your ear while it’s powered on.

• A soft, steady humming or spinning noise is normal.
• Unusual clicking, grinding, or scratching sounds often indicate physical damage inside the drive.

If you can’t tell exactly what’s wrong after these checks, that’s fine! Just start with the first fix in the next section and follow the steps in order.

Six Stepwise Fixes to Resolve Cyclic Redundancy Check (CRC) Errors

Step 1: Check and Replace the Cable or Port

• Unplug the SATA, USB, or other cables attached to your drive. Also, unplug the network cables if you are trying to transfer data over a network.
• Inspect the connectors carefully for bent pins, dirt, and rust.
• Replace the cables and try again.

Step 2: Test the Drive on Another Computer or Powered Dock

• If possible, connect the external drive to another PC, preferably a desktop with a SATA port or a high-quality, powered USB dock.
• If the drive works fine there and files copy without errors, the original PC’s controller or USB ports may be at fault.

Back up your important data immediately once this works.

Step 3: Run CHKDSK to Repair File-System Errors

• Open Command Prompt as administrator (type cmd in the Windows search bar, right-click on the Command Prompt icon, and choose Run as administrator).

• Type the following command and press Enter: chkdsk X: /r /f

Replace X with your drive letter (e.g., if your drive’s letter is “D,” enter the command: chkdsk D: /r /f).

• Let the scan run completely; it may take anywhere between a few minutes and a few hours depending on your drive’s capacity and health.

Why? This command finds and repairs corrupted file-system errors and marks bad sectors to prevent further data loss.

• Reboot your system and try again.

Step 4: Repair Windows System Files With SFC and DISM

• If CRC errors persist, open Command Prompt again (as administrator).
• Run the System File Checker (SFC) utility by typing: sfc /scannow
• Press enter. Once the scan is completed, restart the system and open Command Prompt again (as administrator).
• Type and run these commands one by one (hit enter after each command):

DISM /Online /Cleanup-Image /CheckHealth

DISM /Online /Cleanup-Image /ScanHealth

DISM /Online /Cleanup-Image /RestoreHealth

• These commands will scan and repair core Windows system files that might be causing checksum mismatches.

Step 5: Use ROBOCOPY to Copy Files Reliably

• Sometimes CRC errors appear during file copy, especially over unstable Wi-Fi connections.
• Open Command Prompt and run:

robocopy “E:\Source” “F:\Dest” /E /Z /R:2

Replace “E:\Source” and “F:\Dest” with your source and destination folder paths.

• The /Z switch allows automatic retries if any packets drop during transfer.
• When the copy ends with “0 Failed,” you’ll know it was successful.

Step 6: Assign a New Drive Letter

• Open Disk Management (press Win + R, type msc, and press enter).
• Right-click the problematic partition and select Change Drive Letter and Paths. Assign a new letter and click OK.

• Restart your computer and check if the issue is resolved.

If you have carefully followed all these six steps and still face Cyclic Redundancy Check errors while accessing or transferring important files, it may be time to seek professional help.

Try Professional Data Recovery Software

Download and run Stellar Data Recovery for Windows. The Deep Scan option reads the drive sector-by-sector, rebuilds files by their signatures, and can recover data from CRC error drives right at home.

But software-based solutions have their limitations. If the drive is physically damaged or severely corrupted, even powerful tools might not work. To overcome this, you need to consult a data recovery service provider.

Call In Professional Help – CRC Error Data Recovery

Recurring CRC errors may point toward severe damage or corruption, and you may even face the possibility of permanent data loss. If you detect any symptoms of hard disk failure or SSD failure, or if you have tried all DIY methods listed above without success, it’s time to contact a professional data recovery lab immediately.

What happens in a Stellar Data Recovery Lab?

Stellar Data Recovery experts work in special, ultra-clean environments (called Class 100 cleanroom). Here’s what they do.

• They safely open your hard drive and replace any malfunctioning internal parts with new ones, with surgical precision.
• They use advanced tools to create a clone of your drive.
• From this “clone,” they skillfully rebuild your lost files.

The possibility of getting all your data back is high for drives with CRC errors—if you seek timely help from HDD data recovery experts. Remember, your photos, documents, and other data are usually still present in the drive, just in a part of the drive that the computer can no longer read by itself. And the experts at Stellar can access those parts and recover your data.

Frequently Asked Questions

1. How do I fix a Cyclic Redundancy Check error quickly?

Run CHKDSK /r /f, swap to a fresh USB/SATA cable, and try copying with robocopy /Z. A majority of cases can be resolved with these three steps.

2. What is Cyclic Redundancy Check in computer networks?

A CRC is a remainder produced when a data block, treated as a binary polynomial, is divided by a fixed generator polynomial. This CRC error detection technique lets network nodes spot even one flipped bit and request a retransmission.

3. What are three common causes of cyclic redundancy check (CRC) errors?

1. Bad sectors or worn-out flash cells.
2. Loose or oxidized cables/ports.
3. Sudden power loss while writing.

All three break the checksum and trigger the familiar Data Error (Cyclic Redundancy Check) dialog.

4. Why does “data error (cyclic redundancy check)” appear when initializing a disk?

Windows writes partition info during initialization; unreadable sectors at the start of the disk make the checksum mismatch. Replace the cable, try another PC, and—if SMART shows reallocated sectors—recover important data before formatting the drive.

5. Is CRC error detection in computer networks the same as on a hard disk?

Yes, and no. Both use polynomial division for detection, but drives store the CRC on media, while networks discard corrupted packets and resend them. The math is identical; only the recovery method differs.