HELP!! ntoskrnl.exe causes pc to restart.

My pc restarts on its own whenever i am playing games like Assassins creed or smaller like this day mounte & blade.Sometimes it happens while i am watching youtube videos.I have downloaded WhoCrashed and on every restart ntoskrnl.exe is the cause of it.Here are two dmp files describing the problem.
Please help me fix.

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Dump File : 120413-13322-01.dmp
Crash Time : 4/12/2013 8:55:47 μμ
Bug Check String :
Bug Check Code : 0x00000124
Parameter 1 : 00000000`00000000
Parameter 2 : fffffa80`05c7a8f8
Parameter 3 : 00000000`00000000
Parameter 4 : 00000000`00000000
Caused By Driver : ntoskrnl.exe
Caused By Address : ntoskrnl.exe+52ebc9
File Description :
Product Name :
Company :
File Version :
Processor : x64
Crash Address : ntoskrnl.exe+52ebc9
Stack Address 1 :
Stack Address 2 :
Stack Address 3 :
Computer Name :
Full Path : C:\Windows\Minidump\120413-13322-01.dmp
Processors Count : 3
Major Version : 15
Minor Version : 9200
Dump File Size : 262.144
Dump File Time : 4/12/2013 8:55:50 μμ
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Dump File : 120413-12667-01.dmp
Crash Time : 4/12/2013 3:24:55 μμ
Bug Check String :
Bug Check Code : 0x00000124
Parameter 1 : 00000000`00000000
Parameter 2 : fffffa80`05c9a8f8
Parameter 3 : 00000000`00000000
Parameter 4 : 00000000`00000000
Caused By Driver : ntoskrnl.exe
Caused By Address : ntoskrnl.exe+52ebc9
File Description :
Product Name :
Company :
File Version :
Processor : x64
Crash Address : ntoskrnl.exe+52ebc9
Stack Address 1 :
Stack Address 2 :
Stack Address 3 :
Computer Name :
Full Path : C:\Windows\Minidump\120413-12667-01.dmp
Processors Count : 3
Major Version : 15
Minor Version : 9200
Dump File Size : 262.144
Dump File Time : 4/12/2013 3:24:58 μμ
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