Windows 7: Random Blue Screen and Crashes

I have a custom built PC. It crashes and gives me a blue screen of death at random times. Here's the last two BlueScreenView minidumps I've gotten tonight:

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Dump File : 030210-34289-01.dmp
Crash Time : 3/2/2010 11:15:08 PM
Bug Check String : PAGE_FAULT_IN_NONPAGED_AREA
Bug Check Code : 0x00000050
Parameter 1 : fffff280`06696930
Parameter 2 : 00000000`00000000
Parameter 3 : fffff800`02ab6a79
Parameter 4 : 00000000`00000007
Caused By Driver : ntoskrnl.exe
Caused By Address : ntoskrnl.exe+71f00
File Description : NT Kernel & System
Product Name : Microsoft® Windows® Operating System
Company : Microsoft Corporation
File Version : 6.1.7600.16385 (win7_rtm.090713-1255)
Processor : x64
Computer Name :
Full Path : C:\Windows\minidump\030210-34289-01.dmp
Processors Count : 3
Major Version : 15
Minor Version : 7600
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Dump File : 030210-27050-01.dmp
Crash Time : 3/2/2010 10:51:11 PM
Bug Check String :
Bug Check Code : 0x00000109
Parameter 1 : a3a039d8`961bd5de
Parameter 2 : b3b7465e`e898a81c
Parameter 3 : fffff800`02e351e0
Parameter 4 : 00000000`00000001
Caused By Driver : ntoskrnl.exe
Caused By Address : ntoskrnl.exe+71f00
File Description : NT Kernel & System
Product Name : Microsoft® Windows® Operating System
Company : Microsoft Corporation
File Version : 6.1.7600.16385 (win7_rtm.090713-1255)
Processor : x64
Computer Name :
Full Path : C:\Windows\minidump\030210-27050-01.dmp
Processors Count : 3
Major Version : 15
Minor Version : 7600
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Does anybody know what this means or what I should do? I feel like I've tried everything!

I've been getting the dreaded " PAGE_FAULT_IN_NONPAGED_AREA PAGE_FAULT_IN_NONPAGED_AREA" crash too but just on my first ColdBoot once a day. After that one time, it's never done it until I have the system off for several hours. A few guys suggested to use the "SFC /verifynow" or "SFC /scannow" command in the advanced command prompt window under accessories. Also it was suggested to try MEMTEST 3.4 to check for errors.