If you’ve encountered Windows ERROR_21, also known as the "Device Not Ready" error, don’t worry — you’re not alone, and this guide will help you troubleshoot and fix it like a pro. This error typically means that Windows is unable to access a specific device, such as a hard drive, USB device, or CD/DVD drive.
In this detailed, easy-to-follow guide, we’ll cover what ERROR_21 means, common causes, and step-by-step solutions you can perform on your own. Whether you’re a tech novice or a savvy user, this article is crafted to help you get your Windows system back on track quickly.
What is Windows ERROR_21?
ERROR_21 is a system error code with the description "Device Not Ready." It often appears when a hardware device, like a hard disk or removable media, isn’t accessible due to a hardware fault, improper connection, or driver issue.
Common Symptoms:
- You try to access a drive or device, but get an error message.
- The device is detected but cannot be used.
- Your system may freeze or throw popups related to the device.
- Unable to read or write data to the specific hardware.
Why Does ERROR_21 Occur?
The most common causes include:
- Faulty or disconnected hardware (e.g., loose cables)
- Outdated, corrupted, or incompatible drivers
- Corrupted system files or registry entries
- Issues with the device’s file system (e.g., bad sectors)
- Malware or software conflicts blocking access
Step-by-Step Guide to Fix Windows ERROR_21
Step 1: Restart Your Computer
It’s simple, but many issues can be resolved by a quick reboot. This clears temporary glitches in hardware communication.
- Save your work.
- Click Start > Power > Restart.
- After reboot, try accessing the device again.
Step 2: Check Physical Connections
If you’re working with external devices:
- Unplug the device, wait 30 seconds, and plug it back in.
- Use a different USB port or cable to rule out faulty connections.
- For internal devices like hard drives, open your PC case (only if comfortable) and check cables are securely connected.
Step 3: Run Windows Hardware and Devices Troubleshooter
Windows has a built-in troubleshooter to diagnose problems:
- Press Windows + I to open Settings.
- Navigate to Update & Security > Troubleshoot > Additional troubleshooters.
- Find and run the Hardware and Devices troubleshooter.
- Follow on-screen instructions.
Step 4: Update or Reinstall Device Drivers
Corrupted or outdated drivers commonly cause ERROR_21.
- Press Windows + X and select Device Manager.
- Find the problematic device (look for yellow warning signs).
- Right-click and select Update driver > Search automatically for updated driver software.
- If updating doesn’t work, right-click and choose Uninstall device.
- Restart your PC to allow Windows to reinstall the driver automatically.
Step 5: Check the Device Status in Device Manager
- Open Device Manager.
- Double-click the device to open Properties.
- Check the Device Status box under the General tab.
- If it reports an error code, search online with the specific code for targeted fixes.
Step 6: Run System File Checker (SFC) and DISM Tools
System file corruption can cause device errors.
- Press Windows + S, type cmd.
- Right-click Command Prompt, select Run as administrator.
-
In the Command Prompt window, type:
sfc /scannow
Press Enter and wait for the scan to complete.
-
If issues persist, run:
DISM /Online /Cleanup-Image /RestoreHealth
- Restart your PC after both scans are complete.
Step 7: Check Disk for Errors
If the error involves a hard drive or USB device, check for disk errors:
- Press Windows + E to open File Explorer.
- Right-click the drive, select Properties > Tools.
- Under Error Checking, click Check.
- Follow prompts to scan and fix file system errors.
Step 8: Scan for Malware and Viruses
Malicious software can block device access.
- Run a full system scan using Windows Defender or a reliable third-party antivirus.
- Remove any detected threats and restart your PC.
Step 9: Test the Device on Another Computer
To rule out hardware failure:
- Connect the device to a different computer.
- If it works fine there, the issue is likely with your Windows setup.
- If it fails, the device might be defective and may require replacement.
Step 10: Restore Your System
If ERROR_21 started recently, System Restore can help:
- Press Windows + S and type Create a restore point.
- Click System Restore, follow the wizard.
- Choose a restore point before the issue started.
- Confirm and let Windows restore your system.
Final Tips and Preventive Measures:
- Keep your drivers and Windows OS updated.
- Safely eject external devices before unplugging.
- Regularly run antivirus scans.
- Backup important data regularly.
Conclusion
Windows ERROR_21 can be frustrating, but with patience and these detailed troubleshooting steps, you can resolve the issue swiftly. Remember, hardware issues often manifest with this error, so always verify your physical connections and test the device on another machine. If all else fails, professional help might be needed.
Did this guide help you fix ERROR_21? Share your experience below or ask questions — we’re here to help!
Optimize your Windows device health by staying informed and proactive. Bookmark this guide for future reference!
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