Motherboard: Asus M4A785-M
Processor: Phenom II X3 710
RAM: OCZ Riper PC2-8500 1066MHz 2GB
OS: XP SP3
From some POINT on whenever I try to shut down the computer, I started getting "STOP: c000021a {Fatal System Error} The Windows Logon Process system process terminated unexpectedly with a status of 0xc00000000 (0x00000000 0x0000000) The system has been shut down." on a blue screen .
Don't recall of any new software installed or harware added prior to this.
Have up to date Kasperski 2010, but it doesn't show any signs of something funny going on.
Ran "sfc /scannow", with no positive outcome.
Can't quite figure out what exactly can be done with Dr. Watson.
Please help.You're most likely infected...

From MSDN:
Quote

0xC000021A: STATUS_SYSTEM_PROCESS_TERMINATED
(Click to consult the online Win XP Resource Kit article, or see Windows 2000 Professional Resource Kit, p. 1561.)
This occurs when Windows switches into kernel mode and a user-mode SUBSYSTEM, such as Winlogon or the Client Server Runtime Subsystem (CSRSS), is compromised. Security can no longer be guaranteed. Because Win XP can’t 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. This Stop message also can occur as a result of malware infestation or when the computer is restarted after a system administrator has modified permissions so that the SYSTEM account no longer has ADEQUATE permissions to access system files and folders.