Stop c000021a Fatal System Error

This is a Windows stop error, (also referred to as “The Blue Screen of Death” or BSOD error or kernel error).

The stop error message usually reads:

What Causes Stop Error c000021a?

Windows STOP c000021a Fatal System Error occurs when the Windows kernel detects that either Csrss.exe or Winlogon.exe service processes have stop responding or have failed to load. When this happens, Windows stops the system completely and then generates the fatal system error message.

There can be many reasons why you are experiencing this error:

• Corrupt or missing hardware drivers
• Faulty hardware (i.e. Memory)
• Windows service pack has failed to install correctly.
• Your computer has corrupted system files either due to a faulty shutdown or virus/malware.
• Windows System Restore failed during the rollback process.
• Third-party software applications on your computer are causing kernel level conflicts.

Known Solutions

NOTE: The solutions listed below are assuming that you are receiving the stop error AFTER Windows is running. There are some cases where users are experiencing the stop error during the system boot procedure and thus cannot get to the Windows desktop to perform the task listed below in order.

Option 1: Make Sure Your PC Drivers Are Updated (DO THIS FIRST!)

• Missing or corrupt drivers are responsible for many bluescreen errors. Before taking the steps below, we recommend you perform a free driver scan with DriverFinder and make sure all your drivers are up-to-date.

Option 2: Run Chkdsk Command

• Run chkdsk: Go to a command prompt and type “chkdsk /f”.

Option 3: Take Out The Battery

• Unplug your computer and take out the battery. (It looks like a watch battery on your motherboard).
• Plug your computer back in and restart it.
• Shutdown your computer and unplug it again.
• Place your battery back in, plug in your computer, and restart it.
• Check to see if your are still receiving the stop error message.

Option 3: Test or Swap Out Your Memory (RAM)

• Bad or faulty RAM is known to cause many bluescreen errors and can usually be replaced for cheap. Before swapping it out, run Memtest86+ to test OVERNIGHT to see if it reports any errors. If you are not comfortable opening your PC and replacing your memory, bring your computer to a qualified technician.

Option 4:  Perform a Windows System Restore

• Press CTRL+SHIFT+ESC on your keyboard to launch Task Manager
• Click on the Application tab and click “New Task” then “Browse”
• Go to C:\Windows\System32\Restore\ folder and and double-click the rstrui.exe file to start system restore
• Your computer should reboot during the process and the stop error should be fixed.
• If your PC is crashing to fast once in Windows, start your computer in Safe Mode by pressing the F8 key during system boot.

Option 5: FOR WINDOWS XP USERS – Repair From Your Windows Disk

• Turn on your computer and put in your Windows XP disk.
• Press f12, or whatever key allows you to enter your boot option screen. Choose the option that allows you to boot from a CD.
• On the next screen there should be two options “Repair” and “Reinstall”. Click Reinstall Windows (your not actually going to reinstall).
• On the next screen, click “Repair” again.
• Follow the instructions on the screen.
• After Windows runs through the repair process, you should be able to get back into Windows and your stop error should be gone.

Option 6: Backup Your Files and Reinstall Windows (Last Resort)

• Backup all your important files either to another hardrive or burn them to a CD/DVD.
• Format your hard drive and reinstall Windows.

To avoid stop errors in the future, always make sure you are running a good anti-virus program and also run Malwarebytes on a normal basis to ensure your PC is not infected, especially if your computer is used by multiple people.