“Corrupted and unreadable”: what Windows is really saying.

Windows uses NTFS to keep track of all files through the Master File Table (MFT), which is essentially a huge index of information regarding each file. In other words, it tells us where each file resides on the hard drive, what the name of the file is and who the owner is. When this error appears, Windows has read a portion of the MFT and/or a particular folder's information and received something from that portion that failed one of its tests. The important thing to remember here is that your documents and photos probably remain in their exact same location as before; however, it is likely that the instructions on how to find them, which were recorded in the MFT and/or folders' record-keeping processes, have become damaged.

There are two different ways that these instructions may have become damaged. First there is the non-threatening way: a half-written write failure (e.g., removing a USB device while saving, loss of power during save, application crashing) results in unfinished entries within the bookkeeping. There is also a much more threatening way: as parts of the physical locations containing the index begin to fail, the corruption represents symptoms of failing hardware dressed up like software problems. Based upon nothing but the error message itself, you have absolutely no idea if your problem is due to a "bookkeeping" issue or if you are experiencing a hardware failure with a software representation. This one piece of information should dictate everything you do going forward.

All the posts on forums say run chkdsk /f. What they leave out is chkdsk does not recover any information. It merely creates a consistent filesystem. Its licence for creating a consistent filesystem allows it to remove any information it cannot create consistency with. Most times when we have an interrupted write problem (the benign version of this error) chkdsk will resolve your minor issues, files reappear and most of the time people are happy. This is the side of the coin which has landed heads.

The tails side represents a physical version. When you run chkdsk (and force it to read & write) over a hard drive which has failing sectors for several hours, you are essentially beating your dying drive into even further failure by writing across its weak points. At this point all recoverable but wobbly data will be converted to permanently lost fragments, located in a folder called found.000. This type of problem occurs at least once a week: a drive that needed a carefully created image (£300) now needs miracles. If the drive is slow, hot, noisy, or the error came with other strange behaviour, the coin is loaded against you: don't flip it.

Your first step should always be to triage your drive, rather than the symptoms associated with it. Are there new sounds coming from the drive which weren't before? Was everything on the disk slower than usual? Was the error introduced after a physical shock (knock), or a loss of electrical power? As soon as you find yourself answering 'yes' to any of them, you are on the hardware branch: power down and stop immediately, because the corruption is only a symptom, not the disease.

If you believe your drive has no other issues and that damage occurred as a result of unplugging or crashing, then there would be a strong chance that you're on the logical branch; however, from a professional standpoint, we always suggest you copy before attempting to fix the problem (image the volume first, then perform any repairs against the image and leave the original alone). This is the same process we use when recovering drives and that's why our version of this job will never have a tails scenario. One external drive in our files showed exactly this pattern of unreadable directories, the architecture practice’s Elements, and every drawing came back because nothing was ever "fixed" in place.

In this case the maths behind the error is particularly straightforward. If the data stored on the disk drive is easily replaced then we're happy for you to run chkdsk as above and see if you get the heads outcome. However, if the data isn't easily replaceable then either way our free diagnostic service will tell you which branch you're on without using up your one safe shot: fixed £300 + VAT in the single hard drive category if you need to recover any data; there will be no charge for most jobs unless your files come back, and, once you have a quote, you may drop off your hard drive at Tay House or send us the hard drive via insured post (from any location within the UK).