Blue Screen Error: c000021a Fatal System Error

This error occurs when a user-mode subsystem, such as WinLogon or the Client Server Run-Time Subsystem (CSRSS), has been fatally compromised and security can no longer be guaranteed. In response, the operating system switches to kernel mode. Microsoft Windows cannot run without WinLogon or CSRSS. Therefore, this is one of the few cases where the failure of a user-mode service can shut down the system.

Mismatched system files can also cause this error. This can occur if you have restored your hard disk from a backup. Some backup programs might skip restoring system files that they determine are in use.

Running the kernel debugger is not useful in this situation because the actual error occurred in a user-mode process.

Resolving an error in a user-mode device driver, system service, or third-party application:Because bug check 0xC000021A occurs in a user-mode process, the most common culprits are third-party applications. If the error occurred after the installation of a new or updated device driver, system service, or third-party application, the new software should be removed or disabled. Contact the manufacturer of the software about a possible update.

If the error occurs during system startup, restart your computer, and press F8 at the character-based menu that displays the operating system choices. At the resulting WindowsAdvanced Options menu, choose the Last Known Good Configuration option. This option is most effective when only one driver or service is added at a time. If this does not resolve the error, try manually removing the offending software. If the system partition is formatted with file allocation table (FAT), use an MS-DOS startup disk to gain access to the computer's hard disk. If the system partition is formatted with NTFS file system, you might be able to use Safe Mode to rename or delete the faulty software. If the faulty software is used as part of the system startup process in Safe Mode, you need to start the computer using the Recovery Console in order to access the file. If a newly installed piece if hardware is suspected, remove it to see if this resolves the issue.

Try running the Emergency Recovery Disk (ERD) and allow the system to repair any errors that it detects.

Resolving a mismatched system file problem: If you have recently restored your hard disk from a backup, check if there is an updated version of the Backup/Restore program available from the manufacturer. Make sure the latest Windows Service Pack is installed.

STOP: 0xC000021A <-- read this
http://www.faultwire.com/solutions-fatal_error/STATUS-SYSTEM-PROCESS-TERMINATED-0xC000021A-*1314.html

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Look in the Event Viewer to see if anything is reported about those.
http://www.computerperformance.co.uk/vista/vista_event_viewer.htm

MyEventViewer - Free - a simple alternative to the standard event viewer of Windows.
TIP - Options - Advanced Filter allows you to see a time frame instead of the whole file.
http://www.nirsoft.net/utils/my_event_viewer.html

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This is my generic bluescreen troubleshooter - you can try Safe Mode as suggested in the article
above - repeatedly tap F8 as you boot. Vista disks are probably needed - if you do not have to try
repair you can borrow a friends as they are not copy protected. Also you can buy the physical disks
from the system maker cheap as you already own Windows (you will need these to reinstall if
required). You can also make repair disks on another computer.

Here are some methods to possibly fix the blue screen issue. If you could give the Blue Screen info
that would help. Such as the BCC and the other 4 entries on the lower left. And any other error
information such as STOP codes and info such as IRQL_NOT_LESS_OR_EQUAL or PAGE_FAULT_IN_NONPAGED_AREA and similar messages.

As examples :

BCCode: 116
BCP1: 87BC9510
BCP2: 8C013D80
BCP3: 00000000
BCP4: 00000002

or in this format :

Stop: 0x00000000 (oxoooooooo oxoooooooo oxooooooooo oxoooooooo)
tcpip.sys - Address 0x00000000 base at 0x000000000 DateStamp 0x000000000


This is an excellent tool for posting Blue Screen Error Information

BlueScreenView scans all your minidump files created during 'blue screen of death'
crashes, and displays the information about all crashes in one table - Free
http://www.nirsoft.net/utils/blue_screen_view.html


Many BlueScreens are caused by old or corrupted drivers, especially video drivers however there
are other causes.

You can do these in Safe Mode if needed or from Command Prompt from Vista DVD or Recovery
Options if your system has that installed by the maker.

How to Boot to the System Recovery Options in Windows 7
http://www.sevenforums.com/tutorials/668-system-recovery-options.html

You can try a System Restore back to a point before the problem started if there is one.

How to Do a System Restore in Windows 7
http://www.sevenforums.com/tutorials/700-system-restore.html

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Start - type this in Search Box ->  COMMAND   find at top and RIGHT CLICK  -  RUN AS ADMIN

Enter this at the prompt - sfc /scannow

How to Repair Windows 7 System Files with System File Checker
http://www.sevenforums.com/tutorials/1538-sfc-scannow-command-system-file-checker.html

How to analyze the log file entries that the Microsoft Windows Resource Checker (SFC.exe) program
generates in Windows Vista cbs.log (and Windows 7)
http://support.microsoft.com/kb/928228

The log might give you the answer if there was a corrupted driver. (Does not tell all the possible
driver issues).

Also run CheckDisk so we can rule out corruption as much as possible.

How to Run Check Disk at Startup in Windows 7
http://www.sevenforums.com/tutorials/433-disk-check.html

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Often updating drivers will help, usually Video, Sound, Network Card  (NIC), WiFi, 3rd party
keyboard and mouse, as well as other major device drivers.

Manually look at manufacturer's sites for drivers - and Device Maker's sites.
http://pcsupport.about.com/od/driverssupport/ht/driverdlmfgr.htm

Installing and updating drivers in Windows 7 (updating drivers manually using the methods above
is preferred to ensure the latest drivers from System maker and Device makers are found)
http://www.sevenforums.com/tutorials/43216-installing-updating-drivers-7-a.html

How To Disable Automatic Driver Installation In Windows Vista - Drivers
http://www.addictivetips.com/windows-tips/how-to-disable-automatic-driver-installation-in-windows-vista/
http://technet.microsoft.com/en-us/library/cc730606(WS.10).aspx

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How to fix BlueScreen (STOP) errors that cause Windows Vista to shut down or restart
unexpectedly
http://support.microsoft.com/kb/958233

Troubleshooting Vista Blue Screen, STOP Errors (and Windows 7)
http://www.chicagotech.net/vista/vistabluescreen.htm

Understanding and Decoding BSOD (blue screen of death) Messages
http://www.taranfx.com/blog/?p=692

Windows - Troubleshooting Blue Screen Errors
http://kb.wisc.edu/page.php?id=7033

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In some cases this might be required.

StartUp Repair from Recovery Options or Windows 7 disk

How to Run a Startup Repair in Windows 7
http://www.sevenforums.com/tutorials/681-startup-repair.html

How to Boot to the System Recovery Options in Windows 7
http://www.sevenforums.com/tutorials/668-system-recovery-options.html

How to Create a Windows 7 System Repair Disc
http://www.sevenforums.com/tutorials/2083-system-repair-disc-create.html

Hope this helps.