Test your memory. Best method is to run this overnight and get 5 or more passes out of it.
RAM - Test with Memtest86+
Also you should probably check windows files (this is a quick one you can actually do it first if you want)
SFC /SCANNOW Command - System File Checker
sadly given the completely random nature of the crash reports I'm thinking memory for the moment.
a random dump (they're all completely different)
Code:
PFN_LIST_CORRUPT (4e)
Typically caused by drivers passing bad memory descriptor lists (ie: calling
MmUnlockPages twice with the same list, etc). If a kernel debugger is
available get the stack trace.
Arguments:
Arg1: 00000099, A PTE or PFN is corrupt
Arg2: 00034d03, page frame number
Arg3: 00000002, current page state
Arg4: 00034cfc, 0
Debugging Details:
------------------
BUGCHECK_STR: 0x4E_99
CUSTOMER_CRASH_COUNT: 1
DEFAULT_BUCKET_ID: VISTA_DRIVER_FAULT
PROCESS_NAME: taskhost.exe
CURRENT_IRQL: 2
LAST_CONTROL_TRANSFER: from 82d2a51f to 82d1ef2c
STACK_TEXT:
afe387b8 82d2a51f 0000004e 00000099 00034d03 nt!KeBugCheckEx+0x1e
afe387d0 82c6b57f 00e29000 c0007150 85f62030 nt!MiBadShareCount+0x24
afe3881c 82c6b9ab 85f17d40 00000200 00000000 nt!MiDeletePteList+0x30f
afe38c84 82cfad62 c0007148 85f17d40 9ebe75a7 nt!MiDecommitPages+0x422
afe38d1c 82c7e1ea ffffffff 027df300 027df314 nt!NtFreeVirtualMemory+0x880
afe38d1c 775970b4 ffffffff 027df300 027df314 nt!KiFastCallEntry+0x12a
WARNING: Frame IP not in any known module. Following frames may be wrong.
027df2d4 00000000 00000000 00000000 00000000 0x775970b4
STACK_COMMAND: kb
FOLLOWUP_IP:
nt!MiBadShareCount+24
82d2a51f cc int 3
SYMBOL_STACK_INDEX: 1
SYMBOL_NAME: nt!MiBadShareCount+24
FOLLOWUP_NAME: MachineOwner
MODULE_NAME: nt
DEBUG_FLR_IMAGE_TIMESTAMP: 4d9fd753
IMAGE_NAME: memory_corruption
FAILURE_BUCKET_ID: 0x4E_99_nt!MiBadShareCount+24
BUCKET_ID: 0x4E_99_nt!MiBadShareCount+24
Followup: MachineOwner
---------