This error means Windows reached the drive but couldn’t make sense of the file system on it — the index that tells it where your files live is damaged. The good news is that the files themselves are usually still there; it’s the map to them that’s broken. Here’s what it means, what not to do, and how the data is recovered.
The drive works, but the file system that indexes it is damaged — often from an improper ejection, a power cut, or bad sectors on a failing disk. The files are usually intact underneath, which is why formatting or forcing repairs is exactly what loses them.
chkdsk on a drive you think is failing. Formatting wipes the index to the files you’re trying to save, and chkdsk on a struggling disk can overwrite recoverable data. If the files matter, image the drive first and recover from the copy.A drive stores two things: your files, and a file system — an index (on Windows, the master file table, or MFT) that records where every file begins and ends. “The file or directory is corrupted and unreadable” means Windows could talk to the drive but found that index damaged, so it can no longer follow it to your files. Crucially, that’s different from the files being gone: in most cases the file data is still sitting on the disk, and only the map to it is broken. That’s why the fix is to rebuild or read around the damaged file system — not to wipe the drive and start again.
The usual trigger is an interruption while the file system was being written — a drive unplugged without ejecting, a laptop that lost power, or a USB stick pulled mid-copy — which leaves the index half-written and inconsistent. The other common cause is bad sectors: as a drive ages, unreadable areas appear, and if one lands in the file-system tables the whole drive can read as corrupt. On an external drive the USB bridge in the enclosure can also be the fault rather than the disk, so it’s worth trying a different cable and port before assuming the worst.
Windows may offer to format the drive, or suggest chkdsk. Both can make things worse. Formatting clears the file system — the exact index you need to reach your files — so it trades a recoverable drive for an empty one. chkdsk can repair a healthy drive with minor corruption, but on a failing disk it forces re-reads and remaps that stress the drive and can overwrite recoverable data while trying to rebuild the tables. If you don’t know the drive is sound, don’t run either. Copy off what still opens, and the moment the drive is slow, clicking, or the error spreads, stop.
The safe route is to image the drive read-only first, then rebuild the file system from that copy — and where the index is too damaged to rebuild, carve the files straight out of the raw data by their signatures. Either way the original drive is never written to. A single hard drive is from £300 +VAT; an external drive is sent whole, since on a WD the encryption key lives on the bridge board; a memory card or USB stick is from £250 +VAT. Every job opens with a free diagnostic and a fixed written quote.
It means Windows could reach the drive but couldn’t make sense of the file system — the index or master file table (MFT) that tells it where files live is damaged. The files themselves are usually still on the disk; what’s broken is the map to them. Bad sectors on a failing drive can also cause it.
Usually not. In most cases only the file system is damaged and the file data is intact underneath, so it can be recovered by rebuilding the file system from a read-only image or carving the data out directly. The files are only at real risk if you format the drive or run repairs that overwrite it first.
If the drive is healthy and the files aren’t critical, chkdsk can sometimes repair the file system. But if the files matter, recover them first — copy off what still opens, and if the drive is slow, clicking, or the error spreads, stop and have it imaged read-only. Never format the drive to clear the error if you still want the data.
Only on a drive you know is healthy. On a failing drive, chkdsk forces re-reads and remaps that stress the disk and can overwrite recoverable data while trying to repair the file system. If you’re not sure the drive is sound, image it first and recover from the copy, not the original.
Most often because it was unplugged mid-write or lost power, corrupting the file system, or because bad sectors have appeared on an ageing disk. The USB bridge can also be at fault. Try a different cable and port; if it persists, send the whole unit — on a WD the key lives on the bridge board, so the bare disk is no use alone.
The files are usually still there under a broken file system. Before you format or run repairs, send it in and we’ll image it read-only and rebuild the files from the copy — free diagnostic, fixed quote before any work.