The drive read something and the maths did not add up — what came back does not match the check value stored alongside it. That points at several possible causes, and only one of them is a dying disk.
Every sector carries a check value. When a read produces data that fails that check, the drive reports a cyclic redundancy check error rather than handing you data it knows is wrong.
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.Drives write a cyclic redundancy check alongside the data in each sector — a value computed from the contents. On every read the drive recomputes it and compares. If they disagree, the data coming back is not what was written, and rather than pass it to you silently the drive raises a CRC error.
That is the drive behaving correctly. It is a reporting mechanism, not a diagnosis, which is why the same message covers a marginal cable and a dying platter.
Cable or connection. A marginal SATA or USB cable corrupts data in transit, and the drive reports CRC because what arrived does not match. Free to test: swap the cable and the port. On externals this is genuinely common. The USB bridge on an external enclosure can do the same thing as it starts to fail. Bad sectors — the disk surface can no longer reliably hold data in that spot. This is the commonest cause on an internal drive and the one that tends to spread. File-system corruption, where the structure pointing at the data is damaged rather than the data itself.
The pattern tells you a lot: one error that never returns is usually transient; errors that recur, multiply, or cluster in large files point at the surface.
chkdsk /r reads every sector looking for bad ones, which on a failing drive is hours of the exact stress that accelerates the failure. Worse, its job is a consistent file system rather than your files — it will discard entries it cannot reconcile and relocate data to make the structure valid. On a healthy disk with minor corruption that is fine and often helpful. On a drive with spreading bad sectors it regularly converts a recoverable situation into a much worse one.
Copy the important files off first, starting with the irreplaceable ones and accepting that some may fail to copy. Then work out which cause you have: swap the cable, try another port and another machine, and listen to the drive. Only once the data is safe should any repair tool touch it.
Where the drive is failing, recovery means imaging read-only past the bad sectors and rebuilding from the copy — a single drive from £300 +VAT after a free 48-hour diagnostic, most jobs no fix, no fee.
The drive read a sector and the data failed its stored checksum, so what came back is not what was written. It is the drive refusing to hand you data it knows is wrong — a report rather than a diagnosis, which is why the same message covers a bad cable and a failing platter.
No. A marginal cable, a failing USB bridge on an external, or file-system corruption all produce it. Swapping the cable and trying another port costs nothing and resolves a fair share of cases, particularly on external drives.
Not as a first step. On a drive with failing sectors, chkdsk /r reads every sector — hours of exactly the wrong stress — and it will discard or relocate data to make the file system consistent. Copy your files off first, then repair.
Usually. The drive is imaged read-only with a hardware imager that retries and skips unreadable sectors without stressing the disk, and the files are rebuilt from that image. Whether everything returns depends on how widespread the bad sectors are.
A single drive is from £300 plus VAT after a free 48-hour diagnostic and a written quote, with most jobs no fix, no fee. External drives should be sent complete with their enclosure.