"You need to format the disk in drive E: before you can use it"? Don't click Format yet
You plug in a stick, card or drive that worked yesterday and Windows says it needs formatting. Click Cancel. Formatting wipes the file list, and your files may well still be there.
Why Windows says this
| Likely cause | Clues | What to do |
|---|---|---|
| Formatted for a Mac (APFS or HFS+) | Used with a Mac or for Time Machine; works fine there | Plug it into the Mac and copy the files off. Reformat as exFAT if it needs to work on both. |
| Formatted by another device | Came from a TV recorder, CCTV box, game console or Linux PC | Those often use their own formats (ext4, XFS or proprietary). Use the original device, or a Linux live USB for ext4. |
| Unplugged mid-write or power cut | Removed without ejecting, laptop died during a copy | Try chkdsk /f (below). If it says RAW isn't supported, recover the files first. |
| Fake-capacity stick | Cheap "2 TB" stick, problems after copying a lot onto it | The stick lies about its size and overwrote earlier files. Test it with H2testw or f3 and bin it. |
| Failing drive | Clicking, slow to appear, disconnects, errors in CrystalDiskInfo | Stop. Every extra attempt can make it worse. Copy or image it first (see clicking drives). |
| Bad USB connection | Front port, hub, worn cable, card reader | Try a rear port and another cable or reader before anything else. |
Try a repair (only if the drive sounds healthy)
Open Command Prompt as administrator and run chkdsk E: /f, swapping in the right letter. It repairs the file system's own structures without formatting. If it replies "CHKDSK is not available for RAW drives", Windows can't find the file system at all: move on to recovery. Don't run chkdsk /r on a drive that clicks or keeps dropping out: it reads every sector and can finish a dying drive off.
Get the files back first
- Don't write anything to the drive, and don't format it, even a quick format.
- TestDisk (free, Windows, Mac, Linux) can often find the lost partition or file system and rewrite it, which brings the drive back exactly as it was. Choose the disk, Analyse, Quick Search, and look for your partition with its files listed.
- PhotoRec (same download) ignores the file system and pulls files out by recognising them. It finds photos, videos and documents well but loses folder names and file names. Save them to a different drive.
- For a drive with physical problems, make an image with
ddrescuefirst and recover from the image. - If the files are irreplaceable and the drive is damaged, a professional recovery service is safer than repeated tries.
When it's fine to format
If the drive is new, has nothing you need, or you've already copied everything off, click Format. Pick exFAT for a stick or drive shared between Windows, Mac, cameras and TVs, or NTFS if it only ever plugs into Windows. Untick Quick Format if you want Windows to check every part of the drive as it goes (slower). If the same drive goes RAW again soon after, treat it as failing.
On a Mac
The Mac version says "The disk you inserted was not readable by this computer" with Initialize, Ignore and Eject buttons. Initialize means format. Choose Ignore, then open Disk Utility and run First Aid on the drive. A drive formatted NTFS by Windows can be read but not written on a Mac, which is a different problem: see external drive read-only on a Mac.
Related
Pending and uncorrectable sectors · SMART report explainer · USB stick or external drive not showing up · SD card not showing up · Drive clicking or beeping · New SSD not showing up · What is a file system? (Wirebook)
Questions
What does "You need to format the disk before you can use it" mean?
Windows can't read the drive's file system, so it sees the drive as RAW and offers to format it. Formatting would erase the file list, so cancel and recover the files first if you need them.
Can I get my files back from a drive that says it needs formatting?
Often, yes. Don't format it. Try chkdsk /f if the drive is healthy, or use TestDisk to restore the partition or PhotoRec to copy files out onto another drive.
Why does my Mac drive ask to be formatted on Windows?
Macs usually format drives as APFS or HFS+, which Windows can't read. Copy the files off on the Mac, and use exFAT for drives shared between both.
What does "CHKDSK is not available for RAW drives" mean?
Windows can't find a file system on the drive at all, so chkdsk has nothing to repair. Use a recovery tool such as TestDisk or PhotoRec instead.
Is it safe to click Format?
Only if there's nothing on the drive you need, or you've already copied it off. Formatting a drive with files you want makes recovery harder.
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