How to fix the Windows System Error 21 ERROR_NOT_READY

Symptoms of Code 21 - ERROR_NOT_READY

When processing, Windows send System Error codes to tell the user the kind of problem happening to the computer. They appear at unexpected instances so it is difficult to detect unless one analyzes the error message that comes with it. Windows System Error codes are symptoms to other problems happening to the computer, and since they are, users need to consider the error message, the time and the processes running while it occurred.

(For illustrative purposes only)

Causes of ERROR_NOT_READY - Error 21

Windows system errors can be caused by software or hardware breakdown. Sometimes, your software is not working in consistency with the hardware because of changes or general hardware failures. At some instances, users might have installed conflicting drivers or the OS got corrupted. Perhaps a component had some abnormal power surge which can damage parts and affect its operation. Different kinds of factors may have happened which caused the system to display a System error at certain periods of computer usage. Problems with software and hardware, of course, easily resolved if user can easily pinpoint the portion that are causing the failure. To address problems with these kinds of error, try the following repair methods.

Repair Methods

If a repair method works for you, please click the upvote button to the left of the answer, this will let other users know which repair method is currently working the best.

Please note: Neither ErrorVault.com nor it's writers claim responsibility for the results of the actions taken from employing any of the repair methods listed on this page - you complete these steps at your own risk.

Method 3 - Roll Back your Driver

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You may also go back to the original driver your computer came with. To do that:

• On Device Manager, find the problematic driver.
• Right click the device and click Properties.
• When you see the Properties window, click the Driver tab.
• You will see the Roll Back Driver button, click that.
• Confirm the rollback by clicking Yes when you see a question that says "Are you sure you would like to roll back to the previously installed driver software?"
• Restart your computer after this.

Method 4 - Use System Restore

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For Window 7

• Click Start > All Programs > Accessories > System Tools
• Click System Restore and then click Next.
• Choose your restore point when you know your computer is doing fine
• Keep clicking Next and the click Finish
• It will take time so be patient, wait for the operation to completely stop

For Windows 8, 8.1 or 10

• Right-click the Start button, then click System.
• Once in System window, click System and Security.
• Tap System and on the left side, click System protection.
• Click System Restore, follow the instruction to select your restore point and then click Next until you see the Finish button.
• Wait for the restore process to finish.

Method 1 - Repair Corrupted or Missing System Files

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System File Checker - this tool works pretty much like a registry checker but this helps you find and repair corrupted or missing system files so it takes a bit longer to run

• To run the command, open elevated Command prompt by typing it on the search window, then right clicking Command Prompt and choosing run as administrator
• Type sfc /scannow on the prompt and wait until verification process is successfully completed

Run Checkdisk - Chkdsk repairs many inconsistencies with the OS. System errors may also be repaired using this utility. To run it,

• Open Command Prompt by typing it on the search box, then when you see the result on the list overhead, right click on it and choose, Run as Administrator
• Your system might say you cannot run it at the moment because you are still processing data, and will ask you if you want to run it before the next startup, just click y for yes and then exit the screen and reboot the computer
• Once the computer reboots, you will see checkdisk running outside of Windows, just let it finish till it gives you a report of what was found, fixed or marked
• Exit the window and the let your computer reboot normally.

Method 2 - Update or Reinstall your Driver

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Changes done to your computer can mess up your driver. If that happens, you can either reinstall your driver or update it. To do that, you can do the following.

• If you received a Device Manager error code, take note of the description so you can pinpoint the driver or the component that is causing the error
• Launch device manager by either searching for Device Manager or running "devmgmt.msc"
• Find the driver on the list and right click on it
• Click Uninstall in case you want to reinstall the driver, or Update Driver Software if you are trying to update it.
• You will see a confirmation window, make sure the Delete driver software item is unchecked.
• Click ok then reboot your computer.

You may alternately do this:

• You may manually download the driver from the manufacturer.
• Run it to replace the current driver you are using.
• Once done, let your computer reboot.

Method 5 - Repair reinstall using your OS CD or flash drive

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• The best way to repair your system software is still reinstalling it. Repair reinstall process helps you keep your files as you repair the operating system. Though, you need to make sure you back up your file if you indeed need to clean reinstall your computer. You will need to insert your installation media and restart your computer.
• Access your BIOS, the process differs from one computer model to another, it may be F1, F2, or Del button.
• Once there, go to boot section, set boot to the installation disk and save settings.
• For earlier version of Windows, you may need to tap your keyboard while you wait for the computer to access the installation disk.
• Choose the repair utility first instead of clean installing the OS. This may save you a lot of hassles. However, if the issue continues after rebooting your computer, then just back up files and do the clean reinstall.

Other languages:

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About The Author: Phil Hart has been a Microsoft Community Contributor since 2010. With a current point score over 100,000, they've contributed more than 3000 answers in the Microsoft Support forums and have created almost 200 new help articles in the Technet Wiki.

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