Windows 8 frequently restarts with error code 0xc000021

Original Title : Window 8 Error



my new samsung ultrabook series 5 is having error code 0xc000021 , the system is keep restarting and trying to repairs, but it failed.


Hi Kaenice,


I would suggest you to try the methods given below and check if it helps, but before we proceed, please answer the questions given below.


Do you remember making any changes prior to this issue?


Let us follow the methods given below.


Method 1: Try booting the computer in safe mode and perform a clean boot.


Step 1: Let’s boot from the Windows 8 DVD and login in Safe Mode


a) Boot from Windows 8 DVD.

b) After you see a Choose an Option, click on ‘Troubleshoot’.

c) Now click on ‘Advanced Options’ and then on ‘Windows Startup Settings’.

d) Use your arrow keys to go to ‘Safe Mode’ and press Enter.


If you are able to boot in safe mode, please perform clean boot and check if it helps.


Step 2: Perform clean boot.


To help troubleshoot error messages and other issues, you can start Windows 8 by using a minimal set of drivers and startup programs. This kind of startup is known as a "clean boot." A clean boot helps eliminate software conflicts.


Important: Reset the computer to start as usual.


Note: After you have finished troubleshooting, follow these steps to boot to normal startup.


a) Press the ‘Windows + R’ key on the keyboard.

b) In the ‘Run’ windows type ’MSCONFIG’ and click ‘Ok’.

c) On the ‘General’ tab, click the ‘Normal Startup’ option, and then click ‘OK’.

d) When you are prompted to restart the computer, click ‘Restart’.


Method 2: You may try to boot from the Windows 8 DVD and try performing a System Restore from Windows Recovery Environment (WinRE).


To perform System Restore on Windows 8 computer follow these steps:


a)      Restart the Windows 8 computer, press & HOLD Shift+F8, until you see the option Choose an operating system.

b)      When you see the screen Choose an operating system, click on Change defaults or choose other options.

c)      Choose the option Troubleshoot and select Advanced options.

d)      You may choose System Restore from Advanced boot option.


I would suggest you to upload the minidump files if the issue persists, refer to the link given below to upload the minidump files.


Hope the information was helpful, if you have any further queries, feel free to post. We will be glad to assist you.

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Question Info

Last updated October 7, 2020 Views 7,606 Applies to: