What does “data error (cyclic redundancy check)” mean?

That a checksum failed — the value calculated when data was written does not match the value calculated when it was read back. It tells you a read went wrong, not why. The cause can be anything from a marginal cable to a failing platter.

Is a CRC error always serious?

No, and that is what makes it awkward. It can be a faulty cable corrupting data in transit on a perfectly healthy drive, a single sector degraded over years, or a disk in active decline. The checks are quick and worth doing before assuming the worst.

What should I check first?

The cable and the port — two minutes, no risk, and it eliminates the one cause unrelated to your data. Then SMART, to see whether reallocated and pending sector counts are climbing. Then whether it is one file failing or many.

Should I run chkdsk to fix it?

Not before you know the drive is healthy. chkdsk /r reads every sector for hours on a disk that may be struggling, and it repairs by discarding records it cannot reconcile — producing a consistent file system rather than your files.

Can files with CRC errors be recovered?

Frequently. Imaging in graduated passes captures everything that reads immediately, then returns to the difficult regions with longer timeouts. Where a sector genuinely cannot be read, that portion of that file is lost while the rest recovers.

Why does the error only affect one file?

Because the damaged sectors happen to fall within that file. A localised defect on an otherwise sound drive produces exactly that pattern — one file that always fails while everything around it reads perfectly.

CRC · the error explained

A checksum failed. That is all it tells you.

The message names the test that failed rather than the reason — which is why the same error can mean a marginal cable or a dying platter. It is a smoke alarm, not a diagnosis, and the useful next step is working out which.

Corrupted file recovery →01223 655015

Checksum mismatch

Cable, sector or bridge

From £300 +VAT

// the short version

The arithmetic disagreed.

Every sector carries a checksum written alongside it. When what comes back off the platter fails that check, the drive raises this error rather than passing you data it already knows is wrong.

Checksum

What CRC is

Sector

Commonest cause

48 hr

Free diagnostic

£300

From, +VAT

×Don’t run chkdsk /f /r as a first response. On a drive with failing sectors it forces repeated re-reads of exactly the areas that are struggling, and it can relocate or discard data while “repairing” the file system. If the file matters, copy what you can first.

// what CRC actually means

The drive read something, and the maths did not agree.

Every sector written to a disk carries a checksum. When the drive reads that sector back it recalculates the checksum and compares. A cyclic redundancy check error means the two did not match — the data returned is not the data that was written.

This is a hardware-level report rather than a software complaint, and it usually means physical degradation of the surface. It can also mean a failing cable or connection, which is worth eliminating first because it costs nothing.

What it does not mean is that the file is beyond reach. A sector that fails checksum can frequently still be read with repeated attempts or with error correction applied, which is precisely what recovery imaging does and what ordinary copying does not.

// what to do

Three steps, and one thing to avoid.

Try a different cable and port first. SATA and USB cables fail silently and produce exactly this error. Two minutes to eliminate and it resolves a meaningful share of these.

Copy what still reads, now. If most files still open, get them off before anything else. A drive producing CRC errors is degrading and will not improve.

Do not run chkdsk. It writes to the disk it is checking. On a drive with failing sectors that write frequently cannot complete, and it is the most common way a recoverable drive becomes a partial one.

Then stop using it. Every additional hour of service spends readable sectors you may want back.

// questions

Answered.

No. Cables and connections produce identical symptoms. Eliminate those first because they cost nothing to test.

Frequently. Sectors that fail checksum can often be read with repeated attempts and error correction, which imaging does and copying does not.

Decline it if the data matters. It is designed to make a file system consistent, not to preserve your files, and it writes to a disk that is already struggling.

From £300 +VAT for a single drive, fixed in writing after the free 48-hour diagnostic.