BSOD Windows XP Page_Fault_In_Nonpaged_Area Stop: 0x00000050

I was getting the BSOD caused by a driver for Alcohol 120 for a virtual CD drive, so I uninstalled that and everything seemed to work fine.
Now I'm getting the BSOD for something different.
Page_Fault_In_Nonpaged_Area Stop: 0x00000050 (0xFFFEFFB, 0X00000000, 0X8054B5B2, 0X00000000)
The BSOD only happens when I try to do a virus scan, or a registry scan or search the registry. I doesn't happen any other time, ie: playing a game, burning a DVD or watching a movie.
I've tried online virus scans and keep getting the same result, BSOD.
I have swapped out my mem sticks with 2 known good ones, but still keep getting the stop during virus scan caused by : ntoskrnl.exe
Found this from Google, ntoskrnl.exe is a critical process in the boot-up cycle of your computer
Is there a way to repair this file ?

This is the latest mini dump:
------------------------------------------------------------------------------
Microsoft (R) Windows Debugger Version 6.11.0001.404 X86
Copyright (c) Microsoft Corporation. All rights reserved.


Loading Dump File [C:\WINDOWS\Minidump\Mini081309-13.dmp]
Mini Kernel Dump File: Only registers and stack trace are available

Symbol search path is: SRV*c:\symbols*http://msdl.microsoft.com/download/symbols
Executable search path is:
Windows XP Kernel Version 2600 (Service Pack 3) UP Free x86 compatible
Product: WinNt, suite: TerminalServer SingleUserTS
Built by: 2600.xpsp_sp3_gdr.090206-1234
Machine Name:
Kernel base = 0x804d7000 PsLoadedModuleList = 0x8055b1c0
Debug session time: Thu Aug 13 17:06:32.265 2009 (GMT-6)
System Uptime: 0 days 4:24:02.890
Loading Kernel Symbols
...............................................................
................................................................
.......
Loading User Symbols
Loading unloaded module list
..............
*******************************************************************************
*                                                                             *
*                        Bugcheck Analysis                                    *
*                                                                             *
*******************************************************************************

Use !analyze -v to get detailed debugging information.

BugCheck 10000050, {fffefff8, 0, 8054b5b2, 0}


Could not read faulting driver name
Probably caused by : ntoskrnl.exe ( nt!ExFreePoolWithTag+237 )

Followup: MachineOwner
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kd> !analyze -v
*******************************************************************************
*                                                                             *
*                        Bugcheck Analysis                                    *
*                                                                             *
*******************************************************************************

PAGE_FAULT_IN_NONPAGED_AREA (50)
Invalid system memory was referenced.  This cannot be protected by try-except,
it must be protected by a Probe.  Typically the address is just plain bad or it
is pointing at freed memory.
Arguments:
Arg1: fffefff8, memory referenced.
Arg2: 00000000, value 0 = read operation, 1 = write operation.
Arg3: 8054b5b2, If non-zero, the instruction address which referenced the bad memory
      address.
Arg4: 00000000, (reserved)

Debugging Details:
------------------


Could not read faulting driver name

READ_ADDRESS:  fffefff8

FAULTING_IP:
nt!ExFreePoolWithTag+237
8054b5b2 668b4efa        mov     cx,word ptr [esi-6]

MM_INTERNAL_CODE:  0

CUSTOMER_CRASH_COUNT:  13

DEFAULT_BUCKET_ID:  COMMON_SYSTEM_FAULT

BUGCHECK_STR:  0x50

PROCESS_NAME:  Regcleaner.exe

LAST_CONTROL_TRANSFER:  from 8058b724 to 8054b5b2

STACK_TEXT:  
b7fffc24 8058b724 fffefffe 00000000 e10475f8 nt!ExFreePoolWithTag+0x237
b7fffc40 8058c5f6 e3f4e148 e10475f8 e1029614 nt!CmpCleanUpKcbValueCache+0x51
b7fffc54 805882a8 e3f4e148 e18306b8 80568ece nt!CmpCleanUpKcbCacheWithLock+0x19
b7fffc60 80568ece b7fffc80 80568d18 e10475f8 nt!CmpGetDelayedCloseIndex+0x16
b7fffc68 80568d18 e10475f8 e10475f8 00000001 nt!CmpAddToDelayedClose+0xa
b7fffc80 80568d34 e10475f8 b7fffca4 8056a929 nt!CmpDereferenceKeyControlBlockWithLock+0x5d
b7fffc8c 8056a929 e10475f8 00000000 e127a418 nt!CmpDereferenceKeyControlBlock+0x12
b7fffca4 80564777 e127a430 e127a418 00000000 nt!CmpDeleteKeyObject+0x92
b7fffcc0 804e36d5 e127a430 00000000 000001a4 nt!ObpRemoveObjectRoutine+0xe0
b7fffce4 80567847 8600baf8 e1971ea8 861ed8b0 nt!ObfDereferenceObject+0x5f
b7fffcfc 805678b0 e1971ea8 e127a430 000001a4 nt!ObpCloseHandleTableEntry+0x155
b7fffd44 805678fa 000001a4 00000001 00000000 nt!ObpCloseHandle+0x87
b7fffd58 804de7ec 000001a4 018dfb6c 7c90e514 nt!NtClose+0x1d
b7fffd58 7c90e514 000001a4 018dfb6c 7c90e514 nt!KiFastCallEntry+0xf8
WARNING: Frame IP not in any known module. Following frames may be wrong.
018dfb6c 00000000 00000000 00000000 00000000 0x7c90e514


STACK_COMMAND:  kb

FOLLOWUP_IP:
nt!ExFreePoolWithTag+237
8054b5b2 668b4efa        mov     cx,word ptr [esi-6]

SYMBOL_STACK_INDEX:  0

SYMBOL_NAME:  nt!ExFreePoolWithTag+237

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: nt

IMAGE_NAME:  ntoskrnl.exe

DEBUG_FLR_IMAGE_TIMESTAMP:  498c1a18

FAILURE_BUCKET_ID:  0x50_nt!ExFreePoolWithTag+237

BUCKET_ID:  0x50_nt!ExFreePoolWithTag+237

Followup: MachineOwner
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If I can't get this repaired, I'll just re-install the OS.
Thanks in advance.