You’ll be tempted to agree when a drive, USB stick or memory card gives you the option to format it before using it. Don’t do this. This message is telling you that Windows can find the device; however, it cannot read the file system. Formatting would create a brand-new, empty file system on top of the existing one, discarding the index to your files. In most cases, these files are still present. Below we explain what the error signifies, why you shouldn’t format, and how the data is recovered.
The device itself works. It’s simply that Windows cannot read the file system on it, so it asks if you would like to create a new one. That new file system would be placed on top of your files and their index. Formatting the device, or writing to it again, is what turns a recoverable problem into a permanent loss.
A storage device has two layers: your files, and a file system which lists all of your files with their location, so the computer knows where each one is. “You need to format the disk before you can use it”, and cousins like “not accessible” and “the volume does not contain a recognised file system”, mean Windows can see the device but can no longer read that index. So Windows responds by offering a format, which creates a brand-new, empty file system. That is the trap: the new index sits on top of the original data, and once Windows starts writing a fresh file system, the files it replaces become progressively harder to recover. The device isn’t asking to be wiped because it is empty; it’s asking because it can’t read what’s there.
On USB sticks and SD cards, it usually comes down to removal during a write operation. If you take a card out of a camera, or pull a USB stick out of a laptop while it is still being written to, the file system is left half-written and therefore unreadable. The other common reason is flash wear. Cards and sticks have a limited number of write cycles, and as they wear, parts of the file system may become unreadable and the entire device reads as RAW. Hard drives and external drives suffer the same thing due to power cuts, improper ejection, or bad sectors falling into the file-system tables. On an external drive, a failing USB bridge can mimic it too, so trying a different cable and port is always worth the effort first.
A format does not eradicate data from a device so much as lay a new, empty file system across it. On a hard drive, memory card or USB stick, a quick format mostly just replaces the index, so data can often still be carved back afterwards, but it makes recovery harder and less complete, and any use you make of the device after formatting starts filling up the space where your old files were. With an SSD it’s worse: a format can activate TRIM, which tells the drive to discard your old data for good. Memory cards and USB sticks do not have TRIM, but a format still writes over the index that you need. Whatever the device, recover your data before you format, never afterwards.
First the device is imaged read-only, so nothing is written to it. Then the file system is rebuilt from this copy, or if it is too damaged, the files are carved out directly from the raw data by their signatures. A memory card or USB stick costs from £250 +VAT; a single hard drive costs from £300 +VAT; an external drive is sent whole, because on a WD the encryption key resides on the bridge board, and the bare disk is no use on its own. Every job commences with a free diagnostic and a fixed written quote.
No, not if you want to keep your data. The prompt appears because Windows can see the drive, but it cannot read its file system, so it offers to build a new, empty one, which destroys the index to your existing files. Most of the time the files are still there. Recover them first, then you can format later if you still need to.
Nearly all of the time it’s because the card or stick was removed while it was still being written to (which corrupts the file system), or because the flash is wearing out and part of the index can no longer be read. However, the card or stick often still holds the actual data. Do not use it further, and avoid formatting, as continued write activity is what overwrites recoverable files.
Yes, most likely. The device is imaged read-only and then the file system is rebuilt from this copy, or the files are carved out of the raw data directly. A memory card or USB stick costs from £250 +VAT and a single drive from £300 +VAT, after a free diagnostic. The key is not to format it or keep writing to it first.
When you format a device, you replace the existing file system with a blank one. In the case of a hard drive, memory card or USB stick, a quick format mostly replaces just the index (or catalogue), so the data can often still be carved back, but it does make recovery harder. If you format an SSD, it can trigger TRIM, which discards the old data for good. Either way, please recover your data before you format.
Windows can see the drive but is unable to open its file system, typically shown as ‘not accessible’ or a prompt to format. This is normally due to corruption or bad sectors, not total failure. If an external drive is having problems, try a different cable and port. If the problem continues, please send the entire unit, since on a WD the key lives on the bridge board.
The files are usually intact, sitting under a corrupt file system. Prior to clicking format or continuing to use the device, send it to us and we’ll image it read-only and rebuild your files from the copy, with a free diagnostic and a fixed quote prior to any work.