BSOD on boot

My laptop previously had Windows 7 32bit on it, it had been running fine. Yesterday I did a clean install to 64bit Pro. However, now sometimes when booting I receive a blue screen prior to the logon screen. The bsod doesn't occur everytime, just randomly. I'm just wondering if anyone had any idea what the problem is

The minidump is below.

Code:

WINLOGON_FATAL_ERROR (c000021a)
The Winlogon process terminated unexpectedly.
Arguments:
Arg1: fffff8a003b84b10, String that identifies the problem.
Arg2: 0000000000000000, Error Code.
Arg3: ffffffffc0000001
Arg4: 0000000000100448

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


BUGCHECK_STR:  0xc000021a_0

ERROR_CODE: (NTSTATUS) 0xc000021a - {Fatal System Error}  The %hs system process terminated unexpectedly with a status of 0x%08x (0x%08x 0x%08x).  The system has been shut down.

EXCEPTION_CODE: (NTSTATUS) 0xc000021a - {Fatal System Error}  The %hs system process terminated unexpectedly with a status of 0x%08x (0x%08x 0x%08x).  The system has been shut down.

EXCEPTION_PARAMETER1:  fffff8a003b84b10

EXCEPTION_PARAMETER2:  0000000000000000

EXCEPTION_PARAMETER3:  ffffffffc0000001

EXCEPTION_PARAMETER4: 100448

ADDITIONAL_DEBUG_TEXT:  initial session process or

CUSTOMER_CRASH_COUNT:  1

DEFAULT_BUCKET_ID:  VISTA_DRIVER_FAULT

PROCESS_NAME:  smss.exe

CURRENT_IRQL:  0

LAST_CONTROL_TRANSFER:  from fffff80002cd0c6e to fffff800028735c0

STACK_TEXT:  
fffff880`02e534e8 fffff800`02cd0c6e : 00000000`0000004c 00000000`c000021a fffff880`02e53608 fffffa80`04a27c20 : nt!KeBugCheckEx
fffff880`02e534f0 fffff800`02ac0f71 : fffffa80`04f30eb6 fffff880`02e53ca0 00000000`00000100 fffffa80`0498c160 : nt!PoShutdownBugCheck+0xae
fffff880`02e53570 fffff800`028bdd84 : 00000000`00000000 00000000`00000004 00000000`00000000 00000000`005af401 : nt!ExpSystemErrorHandler2+0x5e1
fffff880`02e537a0 fffff800`02ca3f31 : 00000000`c000021a 00000000`00000004 00000000`00000001 fffff880`02e53b58 : nt!ExpSystemErrorHandler+0xd4
fffff880`02e537e0 fffff800`02ca57a3 : 00000000`c000021a fffffa80`00000004 fffff8a0`00000001 fffff880`02e53b58 : nt!ExpRaiseHardError+0xe1
fffff880`02e53b10 fffff800`02872813 : fffffa80`048b3b60 00000000`00000001 00000000`005af3f8 fffff800`02b86294 : nt!NtRaiseHardError+0x1a1
fffff880`02e53bb0 00000000`770809ea : 00000000`00000000 00000000`00000000 00000000`00000000 00000000`00000000 : nt!KiSystemServiceCopyEnd+0x13
00000000`005af3d8 00000000`00000000 : 00000000`00000000 00000000`00000000 00000000`00000000 00000000`00000000 : 0x770809ea


STACK_COMMAND:  kb

FOLLOWUP_IP: 
nt!ExpSystemErrorHandler2+5e1
fffff800`02ac0f71 cc              int     3

SYMBOL_STACK_INDEX:  2

SYMBOL_NAME:  nt!ExpSystemErrorHandler2+5e1

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: nt

IMAGE_NAME:  ntkrnlmp.exe

DEBUG_FLR_IMAGE_TIMESTAMP:  4e02aa44

FAILURE_BUCKET_ID:  X64_0xc000021a_0_nt!ExpSystemErrorHandler2+5e1

BUCKET_ID:  X64_0xc000021a_0_nt!ExpSystemErrorHandler2+5e1