Today,when i restart my computer.

A Stop c000021a message occur.i have tried to restart computer.After threes times later ,my computer restart nomally.howerev,it will be happened next restart.So,i use google .baidu and Microsoft to find the answer.

i have found the followed information.

http://www.microsoft.com/resources/documentation/Windows/XP/all/reskit/en-us/Default.asp?url=/resources/documentation/Windows/XP/all/reskit/en-us/prmd_stp_mtgk.asp 

Stop 0xC000021A or STATUS_SYSTEM_PROCESS_TERMINATED

The Stop 0xC000021A message occurs when Windows XP Professional switches into kernel mode and a user-mode subsystem, such as Winlogon or the Client Server Runtime Subsystem (CSRSS), is compromised and security can no longer be guaranteed. Because Windows XP Professional cannot run without Winlogon or CSRSS, this is one of the few situations where the failure of a user-mode service can cause the system to stop responding. You cannot use the kernel debugger in this situation because the error occurred in a user-mode process.

A Stop 0xC000021A message can also occur when the computer is restarted after a system administrator has modified permissions in such a way that the SYSTEM account no longer has adequate permissions to access system files and folders.

Interpreting the Message

This Stop message has three parameters:

1. Status code.
2. This value is 0x00000000 (zero).
3. This value is 0x00000000 (zero).

For information about all possible status codes that might be returned, see the Ntstatus.h file of the Windows XP Professional Driver Development Kit (DDK). For more information about the DDK, see the Driver Development Kits link on the Web Resources page at http://www.microsoft.com/windows/reskits/webresources.

Resolving the Problem

The following suggestions are specific to Stop 0x21A errors. For additional troubleshooting suggestions that apply to all Stop errors, see "Stop Message Checklist" later in this appendix.

• Stop 0xC000021A messages occur in a user-mode process and the most common causes are third-party applications. If the error occurred after installing a new or updated device driver, system service, or third-party application, you need to remove, disable, or roll back the driver, or uninstall the new software. Contact the software manufacturer about a possible update.
• System file mismatch caused by partially restoring the system from backup media might cause this error (some backup programs do not restore files that they determine are in use). Always use backup software that is Windows XP Professional compatible.
• If SYSTEM account permissions were altered, follow the procedures below to regain access to the boot partition:
  1. Perform a parallel Windows XP Professional installation onto a separate partition or drive. Do not use the original drive and folder names because the new Windows XP Professional installation overwrites previous settings. Complete the second installation.
  2. In the Run dialog box, in the Open box, type: c:
  3. Right-click the original Windows XP Professional systemroot folder, and then click Properties.
  4. Click the Security tab, and then grant the local SECURITY account full control of the systemroot folder and its subfolders.
  5. Restart the system, and then select the original Windows XP Professional installation from the startup menu.

While,i remembered that before restarting my computer ,i have installed the software-winrar.maybe this is the reason.

i decided to check this problem.i uninstall Winrar.Everything is return normal.