Data Error Cyclic Redundancy Check – External Hard Drive
Windows displays 'Data error (cyclic redundancy check)' when accessing your external drive.
A CRC error means Windows detected data corruption - the data read from the drive doesn't match its checksum. This indicates bad sectors, file system corruption, or cable/connection issues. Some files may be inaccessible while others work fine.
Don't Run CHKDSK /F or /R!
- ×Do not run CHKDSK with /F or /R flags
- ×Do not keep trying to access the same files repeatedly
- ×Do not defragment the drive
- ×Do not use drive repair utilities
- ×Do not continue using the drive for new data
Why this matters: CHKDSK can mark bad sectors as unusable and truncate or delete 'corrupted' files that may actually be recoverable. Running it often makes recovery harder.
Most Likely Causes
Bad Sectors (Physical Damage)
Portions of the platter surface have degraded and can no longer reliably store data. Reads return corrupted data.
File System Corruption
The file system metadata is damaged, causing CRC errors when Windows tries to verify file integrity.
Cable or Connection Issues
Faulty USB cable or port causing data transmission errors that manifest as CRC failures.
Early-Stage Drive Failure
CRC errors across multiple files often indicate the drive is beginning to fail more broadly.
Safe Diagnostic Checks
These checks are non-destructive and safe to perform. Follow them exactly as written.
Try a different cable and port
- Disconnect the drive
- Use a different USB cable (preferably new)
- Connect to a different USB port
- Try a USB 2.0 port if USB 3.0 gives errors
- If CRC errors persist, it's not the cable
Check which files have errors
- Note which specific files give CRC errors
- Are errors on specific files or the whole drive?
- Can you access ANY files successfully?
- Don't retry failed files more than once
If many files have errors, stop using the drive - it may be failing.
When Professional Recovery Is Required
You should seek professional data recovery if any of these apply:
- •CRC errors affect many files or entire folders
- •Drive makes clicking or unusual sounds
- •Errors getting progressively worse
- •Critical files are affected
- •New cable and ports don't help
Our Recovery Process
Turnaround Time
3-7 business days
Success Rate
85-95% depending on bad sector severity
What happens when you bring your drive to us:
- 1Full drive diagnostic including surface scan
- 2Clone drive with bad-sector handling
- 3Bypass unreadable sectors and recover readable data
- 4Multiple read passes on marginal sectors
- 5Extract maximum recoverable data
- 6Verify file integrity
Frequently Asked Questions
Related Guides
CHKDSK Is Not Available for RAW Drives – Data Recovery
When you run CHKDSK, Windows says 'CHKDSK is not available for RAW drives.'
I/O Device Error – External Hard Drive Recovery
Windows displays 'The request could not be performed because of an I/O device error.'
Disk Unknown Not Initialized – Data Recovery
Windows Disk Management shows your drive as 'Unknown' and 'Not Initialized'.
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