This error means that Windows was able to reach the drive, but was unable to make sense of the file system on it: the index that tells it where your files live has been damaged. The good news is that your files are usually still present on the disk, and it’s just the map to those files that is broken. Below is what it means, what you should not do, and how the data is recovered.
The drive functions, but the file system that indexes it is damaged, often because of an improper ejection, a power cut, or bad sectors on a disk that is starting to fail. Usually your files remain intact under the damaged file system, which is why formatting the drive or trying to force repairs is exactly what loses them.
chkdsk on a drive you think is failing. When you format a drive, all of the information about where each of your files is located gets wiped. If you try to run a check disk (chkdsk) on a failing disk, you could end up destroying data that might be recoverable. Therefore, if your files matter, before you attempt to recover your files, you should take an image of the drive (make an exact duplicate) and recover from that copy.A drive contains two main elements: your files, and a file system, which is 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 was able to communicate with your drive but found that index damaged, so it was no longer able to follow it to your files. Most importantly, 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. Thus the fix is to rebuild or bypass the damaged file system rather than wipe the drive and start again.
Interruptions during file write processes (e.g., pulling out a drive without first unmounting it, a laptop losing power, pulling a USB stick during a copy) are the most typical trigger, and leave part of the index written but incomplete, leaving it in an inconsistent state. Bad sector problems are another common source of failure; like most disks, drives degrade over time, and as they do, “bad” or “unreadable” areas develop. When these occur within parts of the file system’s tables, the disk can appear to be completely corrupted. An external drive’s issue could even be due to its USB bridge, and therefore it is wise to test the drive using a different cable and port before determining the disk is at fault.
Depending upon the situation presented by Windows when you attempt to access the drive, you might receive prompts to format the drive, or to run the chkdsk utility. Running either can make matters worse. A format command will wipe the file system from the disk entirely (i.e. the very table you want to use to get back into your files), thus converting a recoverable drive into an empty one. chkdsk may be able to correct minor errors in a working drive that are not serious enough to require replacement, but forcing rereads and remapping on a drive that is failing will stress it further. Additionally, while attempting to rebuild the file system tables, chkdsk may write over potentially recoverable data. Therefore, if you have any doubts as to whether the drive is reliable and safe to access, do not run either program. Copy off whatever files will still open. As soon as the drive slows, clicks or the error spreads, stop immediately.
For the recovery to be done safely, we first image the drive as read-only, then build the file system from the image of the drive. When the index is too broken down for us to build the file system from it, we extract each file individually using its signature from the raw data. Regardless of whether we can build the file system, we do not write anything back to the original drive. A single hard drive ranges in price from £300 +VAT; an external drive is sent whole because the encryption key is located on the bridge board of a WD hard drive; a memory card or USB stick starts at £250 +VAT. Every job begins with a free diagnostic and fixed written quote.
This means that Windows could see the physical device itself, however Windows cannot decipher the file system (the index/MFT) which is what indicates how to find each individual file on the disk. While the files are typically still present on the disk, they may appear to be gone due to damage to the location map for those files. Sometimes it occurs when a failing disk develops bad sectors.
Generally no. Usually only the file system has been corrupted while the file data underneath it generally remains intact, allowing your files to be recovered by either building a new file system from a read-only image of the drive or by extracting the data from each file individually without having to use a file system. Your files should not be at risk unless you decide to format the drive or otherwise cause damage to the drive through repairs which attempt to rewrite the disk before you recover your files.
Running chkdsk may possibly fix some errors in the file system if the drive is good and your files are not mission-critical. On the other hand, if your files are important, recover them first by opening/copying off all the ones that work, and if your drive is performing slowly and/or clicking, or the error continues to spread, stop and get the drive read-only imaged. Do not format the drive to clear up the problem if you intend to keep your data on it.
Only on a good drive. Using chkdsk on a failing drive will force re-reads and remaps, making it even harder for the disk, and can overwrite data that could have been recovered during the file system repair attempt. Do not run chkdsk unless you’re positive about the health of the drive; if there’s any doubt at all, first make a copy of the drive, then recover from the copy (never from the source).
This usually occurs when either the drive has been removed while writing to it, or some type of loss of power occurred to the drive. It could occur because of growing bad sector areas on the ageing hard drive. The USB bridge itself might also contribute to the problem. First, before sending anything in, try another cable and port. If this doesn’t resolve the issue, please ship us the whole unit. On a Western Digital unit, the key to accessing the files rests on the bridge board, therefore simply removing the bare disk from the housing won’t allow recovery of your files.
In most cases, the files are intact but sit under a damaged file system. Prior to formatting or running any repairs, send it in and we’ll take a read-only image of the data, then rebuild your files from the copy, with a free diagnostic and a fixed quote prior to beginning any work.