First try to go in to the Safe mode by holding down the F5 key on start up if it goes to Safe mode go to Start menu choose
all programs then Accessories then System Tools choose
System Restore then choose a restore point, your system will restore the date you choose.
The STOP 0xC000021A error occurs when either Winlogon.exe or Csrss.exe fails. When the Windows NT kernel detects that either of these processes has stopped, it stops the system and raises the STOP 0xC000021A error. This error may have several causes. Among them are the following:
Mismatched system files have been installed.
A Service Pack installation has failed.
A backup program that is used to restore a hard disk did not correctly restore files that may have been in use.
An incompatible third-party program has been installed.
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To troubleshoot this problem, you must determine which of these processes failed and why.
To determine which process failed, register Dr. Watson as the default system debugger (if it is not already the default debugger). Dr. Watson for Windows NT logs diagnostic information about process failures to a log file (Drwtsn32.log). Also, you can configure this program to produce memory dump files of failed processes that you can analyze in a debugger to determine why a process fails.
To set up Dr. Watson to trap user-mode program errors, follow these steps:
At a command prompt, type System Root\System32\Drwtsn32.exe -I, and then press ENTER.
This command configures Dr. Watson as the default system debugger.
At a command prompt, type System Root\System32\Drwtsn32.exe, and then select the following options:
Append to existing log file
Create crash dump
After the computer restarts from the STOP 0xC000021A error, run Dr. Watson (Drwtsn32.exe).
View the Dr. Watson log to determine what user mode process may be causing the problem.
If the Dr. Watson log does not contain sufficient information to determine the cause of the problem, analyze the User.dmp file to determine the cause of the STOP 0xC000021A error.
If Dr. Watson did not create a User.dmp file for either Winlogon.exe or Csrss.exe, you may have to use a different tool to generate a memory dump file of the process that fails. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
241215 How to use the Userdump.exe tool to create a dump file
Note Follow the instructions in the Knowledge Base article to troubleshoot a process that shuts down with an exception. While you follow these instructions, monitor the following processes to troubleshoot the STOP 0xC000021A error:
Note Most STOP 0xC000021A errors occur because Winlogon.exe fails. This typically occurs because of a faulty third-party Graphical Identification and Authentication (GINA) DLL. The GINA is a replaceable DLL component that Winlogon.exe loads. The GINA implements the authentication policy of the interactive logon model. The GINA performs all identification and authentication user interactions.
It is very common for certain types of remote control software to replace the default Windows GINA DLL (Msgina.dll). Therefore, a good first step is to examine the system to see if it has a third-party GINA DLL. To do this, locate the following registry key:
Value = GinaDLL REG_SZ
If the Gina DLL value is present and if it is anything other than Msgina.dll, it probably means that a third-party product has changed this value.
If this value is not present, the system uses Msgina.dll as the default GINA DLL.
If this error first occurred after the installation of a new or updated device driver, system service, or third-party program, the new software should be removed or disabled. Contact the manufacturer of the software to see if an update is available. For more information about hardware and software vendor contact information, visit the following Microsoft Web site: -
Last known good configuration
If the previous steps in this article do not resolve the problem, start the computer by using the last known good configuration. To start the computer by using the last known good configuration, follow these steps:Note Because there are several versions of Microsoft Windows, the following steps may be different on your computer. If they are, see your product documentation to complete these steps.
Click Start, and then click Shut Down.
Click Restart, and then click OK.
Press F8 at the indicated time:
For an x86-based computer: When a screen of text appears and then disappears , press F8. (The screen of text may include a memory test, lines about the BIOS, and other lines.) There may also be a prompt that tells you when to press F8.
For an Itanium architecture-based computer: After you make your selection from the boot menu, press F8. There may be a prompt that tells you when to press F8.
Use the arrow keys to select Last Known Good Configuration, and then press ENTER.
NUM LOCK must be off before the arrow keys on the numeric keypad will function.
Use the arrow keys to highlight an operating system, and then press E