Quick Answer
Unplug the device, wait 10 seconds, plug it back into a different USB port. If that doesn't work, run chkdsk /f X: (replace X with your drive letter) in Command Prompt as admin.
What This Error Means
When you plug in a USB stick, external hard drive, or even a DVD drive, Windows might pop up the error ERROR_NOT_READY (0X00000015) with the message “The device is not ready.” This happens a lot with flash drives after you yank them out without safely ejecting. Or when a hard drive is dying. Or sometimes just because the USB port is dirty or loose. The real fix is almost always a simple physical check or a quick command.
Step-by-Step Fix
- Unplug the device completely. Take it out of the USB port. If it's an external hard drive, unplug the power cable too if it has one. Wait at least 10 seconds. This clears any leftover electrical charge or stuck data.
- Plug it into a different USB port. Use a port directly on your computer (not a hub). For desktop PCs, use the ports on the back – they're connected straight to the motherboard and give more power. After plugging it in, wait 5 seconds. You should hear the “device connected” sound, and a drive letter should show up in File Explorer. If it does, you're done.
- If no drive appears, open Disk Management. Press Windows Key + X and select “Disk Management.” Look for your device – it might show as “Not Initialized” or “Unallocated.” Right-click the black bar and select “Change Drive Letter and Paths.” Click “Add,” pick a letter, and click OK. After that, the drive should appear in File Explorer.
- Still not ready? Open Command Prompt as administrator. Click Start, type “cmd,” right-click “Command Prompt,” pick “Run as administrator.” Type
chkdsk /f X:(replace X with your actual drive letter – if you're not sure, check Disk Management). Press Enter. This scans and fixes file system errors. It can take a few minutes. When it finishes, close the window and check if the drive works.
Alternative Fixes
If the steps above didn't help, try these one at a time:
- Update the driver. Open Device Manager (right-click Start, select “Device Manager”). Find “Disk drives” or “Universal Serial Bus controllers.” Right-click your device, pick “Update driver,” then “Search automatically for drivers.” Windows will look for a newer driver online. Sometimes a bad driver update causes this error – rolling back the driver (in the same menu, choose “Properties” > “Driver” > “Roll Back Driver”) can fix it.
- Use a different cable. For external hard drives, the USB cable is often the problem. Try a known-good cable. I've seen this error go away with a simple cable swap.
- Test the device on another computer. If it works there, the issue is your PC. If it doesn't, the device itself is dead. For a dead device, you might need data recovery software (like Recuva or EaseUS) or a professional service if the data is critical.
Prevention Tip
Always safely eject USB drives before unplugging them. Right-click the drive in File Explorer and choose “Eject.” Or use the “Safely Remove Hardware” icon in the system tray. This prevents data corruption and keeps your drive ready when you plug it back in. Also, avoid yanking cables – the physical port gets loose over time and causes this error.