BSOD help

Could You please tell me what's wrong?
Here is list of BSODs.

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Dump File : 110109-12776-01.dmp
Crash Time : 1. 11. 2009 15:39:46
Bug Check String : IRQL_GT_ZERO_AT_SYSTEM_SERVICE
Bug Check Code : 0x0000004a
Parameter 1 : 00000000`73c62dd9
Parameter 2 : 00000000`00000002
Parameter 3 : 00000000`00000000
Parameter 4 : fffff880`07673c60
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
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Dump File : 110109-12667-01.dmp
Crash Time : 1. 11. 2009 15:38:08
Bug Check String : BAD_POOL_HEADER
Bug Check Code : 0x00000019
Parameter 1 : 00000000`00000003
Parameter 2 : fffff800`02c5b110
Parameter 3 : fffff800`02c5b510
Parameter 4 : fffff800`02c5b510
Caused By Driver : ehdrv.sys
Caused By Address : ehdrv.sys+16877
File Description :
Product Name :
Company :
File Version :
Processor : x64
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Dump File : 110109-12651-01.dmp
Crash Time : 1. 11. 2009 15:36:36
Bug Check String : SYSTEM_SERVICE_EXCEPTION
Bug Check Code : 0x0000003b
Parameter 1 : 00000000`c0000005
Parameter 2 : fffff800`02d86bbc
Parameter 3 : fffff880`02882490
Parameter 4 : 00000000`00000000
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
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Dump File : 110109-12402-01.dmp
Crash Time : 1. 11. 2009 11:25:12
Bug Check String : PAGE_FAULT_IN_NONPAGED_AREA
Bug Check Code : 0x00000050
Parameter 1 : fffffa00`05476828
Parameter 2 : 00000000`00000000
Parameter 3 : fffff800`02ad04ec
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
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Dump File : 110109-12168-01.dmp
Crash Time : 1. 11. 2009 10:22:55
Bug Check String : IRQL_NOT_LESS_OR_EQUAL
Bug Check Code : 0x0000000a
Parameter 1 : ffffffff`c68d8521
Parameter 2 : 00000000`00000002
Parameter 3 : 00000000`00000001
Parameter 4 : fffff800`02a9be0c
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
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Dump File : 103009-14040-01.dmp
Crash Time : 30. 10. 2009 20:27:25
Bug Check String : BAD_POOL_HEADER
Bug Check Code : 0x00000019
Parameter 1 : 00000000`00000003
Parameter 2 : fffffa80`0395dc40
Parameter 3 : ffffffff`ffffffff
Parameter 4 : fffffa80`0395dc40
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
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I'm getting those BSODs every few hours of runnig PC. I tried complete format, clean install of OS and nothing had helped. All of drivers are the newest from the official sites of manufactures. I am using Windows 7 Home Premium 64bit OS and here is list of my hardware:
MB: ASUS P5Q-E
CPU: Intel Core 2 Quad Q9400 2,66GHz BOX
Pamäť: 2x2GB DDR2 1066MHz TWIN2x C5D DHX
VGA: Gigabyte GV-R487D5-1GD 1GB PCX
HDD: WD6400AAKS 640GB SATA2 16M
Zdroj 500W Fortron Bluestorm II
DVDRW LG GH22LS50

Thanks