How to Repair a SanDisk USB Flash Drive with CMD

You plug in your SanDisk USB drive and Windows can't read it. Maybe it asks you to format it, maybe it shows nothing at all. If that drive holds something important, the order of what you do next really matters.

Most "repair" guides get this dangerously backwards. They walk you through formatting the drive to fix it, which works for the drive but destroys your files. So here's the rule this guide follows: get your data off first, then repair the drive. Recovery and repair are two separate jobs, and doing them in the wrong order is how people lose their thesis.

Part 1: Recover your data first

Before touching anything that writes to the drive, get your files off. Two routes, easiest first.

Unhide files with the attrib command

A common cause of a "blank" SanDisk drive is a virus that flips your files to hidden. They're still there. The attrib command reveals them, and it doesn't write over your data. Plug in the drive, note its letter (say F:), open Command Prompt as administrator and run:

:: Replace F: with your USB drive's letter

:: Clear hidden, read-only and system flags on every file
attrib -h -r -s /s /d F:\*.*

Open the drive afterward. Your files often reappear, sometimes inside a folder with no name. Copy anything you need to your computer right away. If the files show up, you may not need recovery software at all.

Copy files off with free recovery software

If attrib doesn't reveal your files, or the drive is genuinely corrupted, use signature-based recovery. These tools read the raw drive and rebuild files by their signatures, without relying on the broken file system. Free, trusted options are PhotoRec (open source) and Recuva (Windows).

Recover files to your computer or another drive, never back onto the SanDisk drive you're rescuing.

Run a deep scan on the USB drive, preview what it finds, and save everything you care about to a safe location. Once your data is copied off and verified, and only then, move on to repairing the drive.

Part 2: Repair the drive once your data is safe

With your files recovered, you can fix the drive itself. Start with the gentlest option.

Fix file system errors with chkdsk

chkdsk repairs the kind of file system corruption that makes a drive unreadable. Run it on your USB drive letter:

:: Replace F: with your USB drive's letter
chkdsk F: /f

:: /f fixes file system errors. Add /r to also check for bad sectors:
chkdsk F: /f /r

If chkdsk brings the drive back and your files are intact, you're done. If the drive is still unreadable, it needs a full rebuild.

Rebuild the drive with diskpart and format

This is the heavy option. It wipes the drive completely and gives it a fresh, clean file system. Do this only after your data is recovered. Type each line carefully, especially select disk, because choosing the wrong disk number can wipe the wrong drive.

diskpart
list disk            :: find your USB by its size
select disk 2        :: use YOUR USB's number, not necessarily 2
clean                :: wipes the partition table
create partition primary
format fs=fat32 quick   :: use ntfs for files over 4 GB
assign               :: give it a drive letter
exit

After this the drive is blank and working again, ready to reuse. Your recovered files are safe on your computer where you copied them.

Repair without CMD

Prefer a graphical route? Open This PC, right-click the USB drive, choose Properties, open the Tools tab and click Check under error checking. Windows scans and fixes file system problems. To fully reset the drive instead, right-click it and choose Format, but again, only after your data is recovered.

How to stop USB corruption happening again

SanDisk and other USB drives mostly get corrupted from a handful of avoidable habits. Always use Safely Remove Hardware before unplugging, since yanking a drive mid-write is the top cause of corruption. Scan drives for malware before opening them on a shared computer, disable autorun to block infected drives from running code, and don't fill a drive to its absolute limit. Most importantly, keep a second copy of anything that matters, because a USB stick is transport, not a safe long-term home.

Drive fixed and files recovered? Copy those files to a permanent location now, then reuse the drive with a little more confidence. What was on it that you'd want protected next time?