BSOD: c000021a Fatal System Error (with debuglog))

Hi,

I get this BSOD nearly every day. I don't know if this memory_corruption mentioned in the log is caused by hardware or software error.
Can someone help me with the problem?

Opened log file 'c:\debuglog.txt'

Microsoft (R) Windows Debugger Version 6.6.0003.5
Copyright (c) Microsoft Corporation. All rights reserved.


Loading Dump File [M:\Gast\Grundinstall Rev05 Blue Screen\user.dmp]
User Mini Dump File: Only registers, stack and portions of memory are available

Comment: 'Dr. Watson generated MiniDump'
Windows XP Version 2600 (Service Pack 2) UP Free x86 compatible
Product: WinNt, suite: EmbeddedNT SingleUserTS
Debug session time: Mon Sep 18 09:02:32.000 2006 (GMT+2)
System Uptime: not available
Process Uptime: 0 days 0:00:04.000
Symbol search path is: SRV*c:\symbols*http://msdl.microsoft.com/download/symbols
Executable search path is: C:\WINDOWS;C:\WINDOWS\system32;C:\WINDOWS\system32\drivers
..............................................................
This dump file has an exception of interest stored in it.
The stored exception information can be accessed via .ecxr.
(5d0.5d4): Illegal instruction - code c000001d (first/second chance not available)
eax=58f3443c ebx=00000000 ecx=00000021 edx=00000000 esi=6a24ece8 edi=000a5d78
eip=50df91d1 esp=0006daec ebp=0006dc20 iopl=0 nv dn ei pl nz na po nc
cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000606
*** WARNING: Unable to verify checksum for locwin32.dll
*** ERROR: Symbol file could not be found. Defaulted to export symbols for locwin32.dll -
locwin32!NWPrevChar+0x1:
50df91d1 ffff ???
0:000> !analyze -v;r;kv;lmtn;.logclose;q
*** ERROR: Symbol file could not be found. Defaulted to export symbols for lgnwnt32.dll -
ERROR: FindPlugIns 8007007b
*******************************************************************************
* *
* Exception Analysis *
* *
*******************************************************************************

*** ERROR: Symbol file could not be found. Defaulted to export symbols for nwgina.dll -
*** WARNING: Unable to verify timestamp for kernel32.dll
*** ERROR: Module load completed but symbols could not be loaded for kernel32.dll

FAULTING_IP:
locwin32!NWPrevChar+1
50df91d1 ffff ???

EXCEPTION_RECORD: ffffffff -- (.exr ffffffffffffffff)
.exr ffffffffffffffff
ExceptionAddress: 50df91d1 (locwin32!NWPrevChar+0x00000001)
ExceptionCode: c000001d (Illegal instruction)
ExceptionFlags: 00000000
NumberParameters: 0

BUGCHECK_STR: c000001d

DEFAULT_BUCKET_ID: CODE_CORRUPTION

PROCESS_NAME: winlogon.exe

ERROR_CODE: (NTSTATUS) 0xc000001d - {AUSNAHME} Ung ltige Anweisung Es wurde versucht, eine ung ltige Anweisung auszuf hren.

LAST_CONTROL_TRANSFER: from 58f0fc12 to 50df91d1

FAILED_INSTRUCTION_ADDRESS:
locwin32!NWPrevChar+1
50df91d1 ffff ???

STACK_TEXT:
WARNING: Stack unwind information not available. Following frames may be wrong.
0006dc20 58f0fc12 002586b0 7c91056d 0006dd2c locwin32!NWPrevChar+0x1
0006dd34 58f130aa 0006e3cc 0006e3c8 0006dd5c lgnwnt32!NWLoginInit+0xe2
0006e3e8 6a228730 00000000 6a25153c 6a251a78 lgnwnt32!NWLoginUI+0x9a
0006e40c 6a24a54f 00000000 00000000 00000000 nwgina!NwGinaShutdownNotify+0x57f9
0006e428 6a228dcd 00000001 00000001 6a24ece8 nwgina!NwGinaShutdownNotify+0x27618
58f00000 00000000 00000004 0000ffff 000000b8 nwgina!NwGinaShutdownNotify+0x5e96


STACK_COMMAND: ~0s; .ecxr ; kb

CHKIMG_EXTENSION: !chkimg -lo 50 -d !locwin32
!chkimg -lo 50 -d !locwin32
50df9151-50df9161 17 bytes - locwin32!NWLstrcoll+1

[ 44 24 08 8b 4c 24 04 50:8b 45 f4 89 85 60 fd ff ]
50df9163-50df918c 42 bytes - locwin32!NWLstrcoll+13 (+0x12)

[ cc cc cc cc cc cc cc cc:00 6a 00 6a 01 8b 85 64 ]
50df918e-50df91c4 55 bytes - locwin32!NWLstrupr+e (+0x2b)

[ cc cc 56 8b 74 24 08 85:00 8b 85 5c fd ff ff 50 ]
50df91c6-50df91e4 31 bytes - locwin32!NWNextChar+36 (+0x38)

[ cc cc cc cc cc cc cc cc:10 89 85 60 fd ff ff 83 ]
50df91e6-50df91ff 26 bytes - locwin32!NWPrevChar+16 (+0x20)

[ c6 5f 5e 5b c2 08 00 8b:45 fc 50 ff 15 c8 b7 00 ]
50df9201-50df9250 80 bytes - locwin32!NWPrevChar+31 (+0x1b)

[ 3b de 73 11 0f be 46 ff:00 8b 45 fc 50 ff 15 60 ]
251 errors : !locwin32 (50df9151-50df9250)

MODULE_NAME: memory_corruption

IMAGE_NAME: memory_corruption

FOLLOWUP_NAME: memory_corruption

DEBUG_FLR_IMAGE_TIMESTAMP: 0

MEMORY_CORRUPTOR: LARGE

FAILURE_BUCKET_ID: MEMORY_CORRUPTION_LARGE

BUCKET_ID: MEMORY_CORRUPTION_LARGE

Followup: memory_corruption
---------

eax=58f3443c ebx=00000000 ecx=00000021 edx=00000000 esi=6a24ece8 edi=000a5d78
eip=50df91d1 esp=0006daec ebp=0006dc20 iopl=0 nv dn ei pl nz na po nc
cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000606
locwin32!NWPrevChar+0x1:
50df91d1 ffff ???
ChildEBP RetAddr Args to Child
WARNING: Stack unwind information not available. Following frames may be wrong.
0006dc20 58f0fc12 002586b0 7c91056d 0006dd2c locwin32!NWPrevChar+0x1
0006dd34 58f130aa 0006e3cc 0006e3c8 0006dd5c lgnwnt32!NWLoginInit+0xe2
0006e3e8 6a228730 00000000 6a25153c 6a251a78 lgnwnt32!NWLoginUI+0x9a
0006e40c 6a24a54f 00000000 00000000 00000000 nwgina!NwGinaShutdownNotify+0x57f9
0006e428 6a228dcd 00000001 00000001 6a24ece8 nwgina!NwGinaShutdownNotify+0x27618
58f00000 00000000 00000004 0000ffff 000000b8 nwgina!NwGinaShutdownNotify+0x5e96
start end module name
00b80000 00b85000 EmbdTrst EmbdTrst.dll Tue Aug 31 20:04:00 2004 (4134BD90)
01000000 01080000 winlogon winlogon.exe Wed Aug 04 08:14:52 2004 (41107EDC)
0ffd0000 0fff8000 rsaenh rsaenh.dll Wed Jul 07 04:17:12 2004 (40EB5D28)
20000000 20017000 odbcint odbcint.dll Wed Aug 04 09:57:25 2004 (411096E5)
50d00000 50d15000 clnwin32 clnwin32.dll Tue Apr 22 17:26:41 2003 (3EA55F31)
50d20000 50d48000 calwin32 calwin32.dll Tue Apr 22 17:28:19 2003 (3EA55F93)
50d50000 50d97000 netwin32 netwin32.dll Tue Oct 28 04:22:46 2003 (3F9DE106)
50da0000 50dab000 clxwin32 clxwin32.dll Tue Apr 22 17:29:51 2003 (3EA55FEF)
50db0000 50dd9000 ncpwin32 ncpwin32.dll Tue Apr 22 17:26:46 2003 (3EA55F36)
50df0000 50e10000 locwin32 locwin32.dll Tue Apr 22 17:24:36 2003 (3EA55EB4)
58f00000 58f3b000 lgnwnt32 lgnwnt32.dll Mon Nov 24 22:31:48 2003 (3FC278C4)
5ad70000 5ada8000 uxtheme uxtheme.dll Wed Aug 04 09:56:43 2004 (411096BB)
5b860000 5b8b4000 netapi32 netapi32.dll Wed Aug 04 09:56:28 2004 (411096AC)
5d090000 5d127000 comctl32 comctl32.dll Wed Aug 04 09:56:31 2004 (411096AF)
629c0000 629c9000 lpk lpk.dll Wed Aug 04 09:56:26 2004 (411096AA)
6a200000 6a266000 nwgina nwgina.dll Tue Dec 16 19:04:31 2003 (3FDF492F)
6a400000 6a422000 nwginar nwginar.dll Tue Nov 25 18:55:29 2003 (3FC39791)
71aa0000 71aa8000 ws2help ws2help.dll Wed Aug 04 09:57:39 2004 (411096F3)
71ab0000 71ac7000 ws2_32 ws2_32.dll Wed Aug 04 09:57:38 2004 (411096F2)
71ad0000 71ad9000 wsock32 wsock32.dll Wed Aug 04 09:57:51 2004 (411096FF)
71b20000 71b32000 mpr mpr.dll Wed Aug 04 09:56:46 2004 (411096BE)
723d0000 723ec000 winscard winscard.dll Wed Aug 04 09:56:36 2004 (411096B4)
73000000 73026000 winspool winspool.drv Wed Aug 04 09:56:38 2004 (411096B6)
74320000 7435d000 odbc32 odbc32.dll Wed Aug 04 09:57:17 2004 (411096DD)
74d90000 74dfb000 usp10 usp10.dll Wed Aug 04 09:56:42 2004 (411096BA)
755c0000 755ee000 MSCTFIME MSCTFIME.IME Wed Aug 04 09:57:31 2004 (411096EB)
75930000 7593a000 profmap profmap.dll Wed Aug 04 09:56:55 2004 (411096C7)
75940000 75948000 nddeapi nddeapi.dll Wed Aug 04 09:56:24 2004 (411096A8)
75950000 7596a000 wlnotify wlnotify.dll Wed Aug 04 09:56:44 2004 (411096BC)
75970000 75a67000 msgina msgina.dll Wed Aug 04 09:58:01 2004 (41109709)
76360000 76370000 winsta winsta.dll Wed Aug 04 09:56:40 2004 (411096B8)
76390000 763ad000 imm32 imm32.dll Wed Aug 04 09:56:30 2004 (411096AE)
763b0000 763f9000 comdlg32 comdlg32.dll Wed Aug 04 09:56:32 2004 (411096B0)
76600000 7661d000 cscdll cscdll.dll Wed Aug 04 09:56:07 2004 (41109697)
769c0000 76a73000 userenv userenv.dll Wed Aug 04 09:56:41 2004 (411096B9)
76b40000 76b6d000 winmm winmm.dll Wed Aug 04 09:57:10 2004 (411096D6)
76bc0000 76bcf000 regapi regapi.dll Wed Aug 04 09:56:40 2004 (411096B8)
76bf0000 76bfb000 psapi psapi.dll Wed Aug 04 09:56:58 2004 (411096CA)
76c30000 76c5e000 wintrust wintrust.dll Wed Aug 04 09:56:41 2004 (411096B9)
76c90000 76cb8000 imagehlp imagehlp.dll Wed Aug 04 09:56:25 2004 (411096A9)
76d60000 76d79000 iphlpapi iphlpapi.dll Wed Aug 04 09:56:10 2004 (4110969A)
76f50000 76f58000 wtsapi32 wtsapi32.dll Wed Aug 04 09:57:55 2004 (41109703)
773d0000 774d2000 comctl32_773d0000 comctl32.dll Wed Aug 04 09:55:56 2004 (4110968C)
774e0000 7761d000 ole32 ole32.dll Tue Jul 26 06:20:40 2005 (42E5BA18)
776c0000 776d2000 authz authz.dll Wed Mar 02 19:19:56 2005 (422603CC)
776e0000 77703000 shsvcs shsvcs.dll Wed Aug 04 09:56:47 2004 (411096BF)
77920000 77a13000 setupapi setupapi.dll Wed Aug 04 09:56:32 2004 (411096B0)
77a80000 77b14000 crypt32 crypt32.dll Wed Aug 04 09:56:01 2004 (41109691)
77b20000 77b32000 msasn1 msasn1.dll Wed Aug 04 09:57:23 2004 (411096E3)
77b40000 77b62000 apphelp apphelp.dll Wed Aug 04 09:56:36 2004 (411096B4)
77c00000 77c08000 version version.dll Wed Aug 04 09:56:39 2004 (411096B7)
77c10000 77c68000 msvcrt msvcrt.dll Wed Aug 04 09:59:14 2004 (41109752)
77c70000 77c93000 msv1_0 msv1_0.dll Wed Aug 04 09:59:11 2004 (4110974F)
77d40000 77dd0000 user32 user32.dll Wed Mar 02 19:19:56 2005 (422603CC)
77dd0000 77e6b000 advapi32 advapi32.dll Wed Aug 04 09:56:23 2004 (411096A7)
77e70000 77f01000 rpcrt4 rpcrt4.dll Wed Aug 04 09:56:30 2004 (411096AE)
77f10000 77f57000 gdi32 gdi32.dll Thu Oct 06 05:18:28 2005 (43449784)
77f60000 77fd6000 shlwapi shlwapi.dll Fri Oct 21 05:38:07 2005 (4358629F)
77fe0000 77ff1000 secur32 secur32.dll Wed Aug 04 09:56:49 2004 (411096C1)
7c800000 7c8f4000 kernel32 kernel32.dll Wed Aug 04 09:56:36 2004 (411096B4)
7c900000 7c9b0000 ntdll ntdll.dll Wed Aug 04 09:56:36 2004 (411096B4)
7c9c0000 7d1d5000 shell32 shell32.dll Fri Sep 23 05:18:17 2005 (433373F9)
Closing open log file c:\debuglog.txt

 

There are several reasons for this. Anymore the most common:

Failing RAM. This seems highly likely in your case. Test this using a non-XP based memory tester:
http://www.memtest86.com/#download0
http://oca.microsoft.com/en/windiag.asp

Windows Update installed a new device driver
How to disable a service or device that prevents Windows XP from booting
http://support.microsoft.com/default.aspx?scid=kb;EN-US;244905

Occasionally, Windows Updates can cause this problem
I have not heard of a recent issue. In the past these four have at times been blamed:

KB893066
KB890923
KB890859
KB893086

But you would not receive an error out of the blue for these older Hotfixes.