Windows 7: Help me pls from repeat random freeze

I have got my computer bought in Aug, everthing is fine until recently, it has random hang which force restart is needed. In some case, i can have hang in welcome screen
My setting:
i7CPU 870
ASUSTek P7H55-M
8.Gb ram
Nvidia Geforce GTX 460

I got the minidump files as follows:
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Executable search path is:
Unable to load image \SystemRoot\system32\ntoskrnl.exe, Win32 error 0n2
*** WARNING: Unable to verify timestamp for ntoskrnl.exe
*** ERROR: Module load completed but symbols could not be loaded for ntoskrnl.exe
Windows 7 Kernel Version 7600 MP (8 procs) Free x64
Product: WinNt, suite: TerminalServer SingleUserTS Personal
Built by: 7600.16617.amd64fre.win7_gdr.100618-1621
Machine Name:
Kernel base = 0xfffff800`03a65000 PsLoadedModuleList = 0xfffff800`03ca2e50
Debug session time: Sun Dec 19 22:34:27.718 2010 (UTC + 8:00)
System Uptime: 0 days 0:03:01.310
Unable to load image \SystemRoot\system32\ntoskrnl.exe, Win32 error 0n2
*** WARNING: Unable to verify timestamp for ntoskrnl.exe
*** ERROR: Module load completed but symbols could not be loaded for ntoskrnl.exe
Loading Kernel Symbols
...............................................................
................................................................
........................
Loading User Symbols
Loading unloaded module list
......
Unable to load image \SystemRoot\System32\drivers\dxgkrnl.sys, Win32 error 0n2
*** WARNING: Unable to verify timestamp for dxgkrnl.sys
*** ERROR: Module load completed but symbols could not be loaded for dxgkrnl.sys
*******************************************************************************
* *
* Bugcheck Analysis *
* *
*******************************************************************************

Use !analyze -v to get detailed debugging information.

BugCheck 116, {fffffa80068054e0, fffff8800377f028, ffffffffc000009a, 4}

Unable to load image \SystemRoot\system32\DRIVERS\nvlddmkm.sys, Win32 error 0n2
*** WARNING: Unable to verify timestamp for nvlddmkm.sys
*** ERROR: Module load completed but symbols could not be loaded for nvlddmkm.sys
***** Kernel symbols are WRONG. Please fix symbols to do analysis.

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*** ***
*** ***
*** Your debugger is not using the correct symbols ***
*** ***
*** In order for this command to work properly, your symbol path ***
*** must point to .pdb files that have full type information. ***
*** ***
*** Certain .pdb files (such as the public OS symbols) do not ***
*** contain the required information. Contact the group that ***
*** provided you with these symbols if you need this command to ***
*** work. ***
*** ***
*** Type referenced: nt!_KPRCB ***
*** ***
*************************************************************************
*************************************************************************
*** ***
*** ***
*** Your debugger is not using the correct symbols ***
*** ***
*** In order for this command to work properly, your symbol path ***
*** must point to .pdb files that have full type information. ***
*** ***
*** Certain .pdb files (such as the public OS symbols) do not ***
*** contain the required information. Contact the group that ***
*** provided you with these symbols if you need this command to ***
*** work. ***
*** ***
*** Type referenced: nt!KPRCB ***
*** ***
*************************************************************************
*************************************************************************
*** ***
*** ***
*** Your debugger is not using the correct symbols ***
*** ***
*** In order for this command to work properly, your symbol path ***
*** must point to .pdb files that have full type information. ***
*** ***
*** Certain .pdb files (such as the public OS symbols) do not ***
*** contain the required information. Contact the group that ***
*** provided you with these symbols if you need this command to ***
*** work. ***
*** ***
*** Type referenced: nt!_KPRCB ***
*** ***
*************************************************************************
*************************************************************************
*** ***
*** ***
*** Your debugger is not using the correct symbols ***
*** ***
*** In order for this command to work properly, your symbol path ***
*** must point to .pdb files that have full type information. ***
*** ***
*** Certain .pdb files (such as the public OS symbols) do not ***
*** contain the required information. Contact the group that ***
*** provided you with these symbols if you need this command to ***
*** work. ***
*** ***
*** Type referenced: nt!KPRCB ***
*** ***
*************************************************************************
*************************************************************************
*** ***
*** ***
*** Your debugger is not using the correct symbols ***
*** ***
*** In order for this command to work properly, your symbol path ***
*** must point to .pdb files that have full type information. ***
*** ***
*** Certain .pdb files (such as the public OS symbols) do not ***
*** contain the required information. Contact the group that ***
*** provided you with these symbols if you need this command to ***
*** work. ***
*** ***
*** Type referenced: nt!_KPRCB ***
*** ***
*************************************************************************
*************************************************************************
*** ***
*** ***
*** Your debugger is not using the correct symbols ***
*** ***
*** In order for this command to work properly, your symbol path ***
*** must point to .pdb files that have full type information. ***
*** ***
*** Certain .pdb files (such as the public OS symbols) do not ***
*** contain the required information. Contact the group that ***
*** provided you with these symbols if you need this command to ***
*** work. ***
*** ***
*** Type referenced: nt!_KPRCB ***
*** ***
*************************************************************************
*************************************************************************
*** ***
*** ***
*** Your debugger is not using the correct symbols ***
*** ***
*** In order for this command to work properly, your symbol path ***
*** must point to .pdb files that have full type information. ***
*** ***
*** Certain .pdb files (such as the public OS symbols) do not ***
*** contain the required information. Contact the group that ***
*** provided you with these symbols if you need this command to ***
*** work. ***
*** ***
*** Type referenced: nt!_KPRCB ***
*** ***
*************************************************************************
*************************************************************************
*** ***
*** ***
*** Your debugger is not using the correct symbols ***
*** ***
*** In order for this command to work properly, your symbol path ***
*** must point to .pdb files that have full type information. ***
*** ***
*** Certain .pdb files (such as the public OS symbols) do not ***
*** contain the required information. Contact the group that ***
*** provided you with these symbols if you need this command to ***
*** work. ***
*** ***
*** Type referenced: nt!_KPRCB ***
*** ***
*************************************************************************
Probably caused by : nvlddmkm.sys ( nvlddmkm+75a028 )

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Thx pls help me, !!!!!!! I can't use my computer at all!!

Welcome to SF, cpark.

First please fill out your System Specs:

HOW TO FILL OUT YOUR SYSTEM SPECS

In the line at the top of “www.SevenForums.com” you will see UserCP.
That is an abbreviation for User Control Panel.
Click on UserCP.
In the left-hand column, under Your Profile you will see Edit System Spec.
Click on Edit System Spec
You can copy and paste from the output of Speccy, Speccy - System Information - Free Download to fill out much of the info. Be sure to use the Other Info section of your System Specs for such info as your optical drive, your wireless adapter, your speakers, etc.

Next, please do the following:

BSOD Posting Instructions

http://www.sevenforums.com/crashes-debugging/96879-blue-screen-death-bsod-posting-instructions.html