When I click on the Turn Off button, the system restart again. But when I click on Standby button, the system is Turn Off. It shows the c000021a fatal system error. Please solve my problem or give me the suggestion to solve the matter.

Hi Krishna,Did you make any software or hardware changes on your computer prior to this issue?The STOP 0xC000021A error occurs when either Winlogon.exe or Csrss.exe fails. Let’s follow these methods & check if it helps.Method 1If you have any unnecessary external device connected to the machine, you may unplug them & check if the issue persists.Method 2You may also follow this link & check if it helps.Windows XP restarts unexpectedly or restarts when you shut down the computerMethod 3For the fatal error STOP 0xC000021A, you may follow this link.How to troubleshoot a "STOP 0xC000021A" errorHope the information helps. Please post back and let us know.RegardsDebleena SMicrosoft Answers Support EngineerVisit our Microsoft Answers Feedback Forum and let us know what you think.