I just took a look at your old dump again. rdyboost.sys is related to RAM so I would suggest you to try different RAM sticks and do some RAM intensive task or play your games and see if it blue screens again. Memory tests are not always reliable so you should check with new sticks.
If you are overclocking any hardware, STOP. Reset any changed values back to default.
Code:
STOP 0x0000003B: SYSTEM_SERVICE_EXCEPTION
Usual causes: System service, Device driver, graphics driver, ?memory
Code:
Start Menu\Programs\AVG Public:Start Menu\Programs\AVG Public
Remove AVG with its removal tool:
AVG | Download tools and utilities
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Recommended from a strict BSOD perspective, compatibility & stability compared to other antiviruses/internet security software. It is free and lightweight:-

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Run a full scan with both (separately) once downloaded, installed and updated.
Code:
*******************************************************************************
* *
* Bugcheck Analysis *
* *
*******************************************************************************
Use !analyze -v to get detailed debugging information.
BugCheck 3B, {c0000005, fffff88005725c9a, fffff88008d21930, 0}
Probably caused by : atikmdag.sys ( atikmdag+aac9a )
Followup: MachineOwner
---------
2: kd> !analyze -v
*******************************************************************************
* *
* Bugcheck Analysis *
* *
*******************************************************************************
SYSTEM_SERVICE_EXCEPTION (3b)
An exception happened while executing a system service routine.
Arguments:
Arg1: 00000000c0000005, Exception code that caused the bugcheck
Arg2: fffff88005725c9a, Address of the instruction which caused the bugcheck
Arg3: fffff88008d21930, Address of the context record for the exception that caused the bugcheck
Arg4: 0000000000000000, zero.
Debugging Details:
------------------
EXCEPTION_CODE: (NTSTATUS) 0xc0000005 - The instruction at 0x%08lx referenced memory at 0x%08lx. The memory could not be %s.
FAULTING_IP:
atikmdag+aac9a
fffff880`05725c9a 87422c xchg eax,dword ptr [rdx+2Ch]
CONTEXT: fffff88008d21930 -- (.cxr 0xfffff88008d21930)
rax=0000000000000001 rbx=fffff8a00dd3c010 rcx=fffff8a00dd3c338
rdx=0000000800000000 rsi=fffff8a00dd3c120 rdi=fffff8a00dd3c010
rip=fffff88005725c9a rsp=fffff88008d22310 rbp=fffff88008d22390
r8=0000000000000002 r9=0000000000000000 r10=fffff88002f65ca0
r11=0000000000000000 r12=0000000000000000 r13=fffff8a00dd3c150
r14=0000000000000000 r15=0000000000000000
iopl=0 nv up ei pl nz na po nc
cs=0010 ss=0018 ds=002b es=002b fs=0053 gs=002b efl=00210206
atikmdag+0xaac9a:
fffff880`05725c9a 87422c xchg eax,dword ptr [rdx+2Ch] ds:002b:00000008`0000002c=????????
Resetting default scope
CUSTOMER_CRASH_COUNT: 1
DEFAULT_BUCKET_ID: WIN7_DRIVER_FAULT
BUGCHECK_STR: 0x3B
PROCESS_NAME: firefox.exe
CURRENT_IRQL: 0
LAST_CONTROL_TRANSFER: from 0000000000000000 to fffff88005725c9a
STACK_TEXT:
fffff880`08d22310 00000000`00000000 : 00000000`00000000 00000000`00000000 00000000`00000000 00000000`00000000 : atikmdag+0xaac9a
FOLLOWUP_IP:
atikmdag+aac9a
fffff880`05725c9a 87422c xchg eax,dword ptr [rdx+2Ch]
SYMBOL_STACK_INDEX: 0
SYMBOL_NAME: atikmdag+aac9a
FOLLOWUP_NAME: MachineOwner
MODULE_NAME: atikmdag
IMAGE_NAME: atikmdag.sys
DEBUG_FLR_IMAGE_TIMESTAMP: 50d225df
STACK_COMMAND: .cxr 0xfffff88008d21930 ; kb
FAILURE_BUCKET_ID: X64_0x3B_atikmdag+aac9a
BUCKET_ID: X64_0x3B_atikmdag+aac9a
Followup: MachineOwner
---------
2: kd> lmvm atikmdag
start end module name
fffff880`0567b000 fffff880`06191000 atikmdag T (no symbols)
Loaded symbol image file: atikmdag.sys
Image path: \SystemRoot\system32\DRIVERS\atikmdag.sys
Image name: atikmdag.sys
Timestamp: Thu Dec 20 02:38:55 2012 (50D225DF)
CheckSum: 00AC6529
ImageSize: 00B16000
Translations: 0000.04b0 0000.04e4 0409.04b0 0409.04e4 Code:
afd!AfdProcessBufferSend+0x78
fffff880`08d21170 fffff800`02ddf694 nt!_imp_NtOpenSymbolicLinkObject+0x918c
fffff880`08d21178 00000000`00000000
fffff880`08d21180 fffff800`02c19000 nt!KiSelectNextThread <PERF> (nt+0x0)
fffff880`08d21188 fffff800`02c8ded3 nt!KiSystemServiceCopyEnd+0x13
fffff880`08d21190 fffff800`02e9db04 nt!BBTBuffer <PERF> (nt+0x284b04)
fffff880`08d21198 fffff800`02c8dac0 nt!KiSystemServiceHandler
fffff880`08d211a0 00000000`00000000
fffff880`08d211a8 fffff800`02c8db3c nt!KiSystemServiceHandler+0x7c
fffff880`08d211b8 fffff880`04c99e6d dxgkrnl!_GSHandlerCheck_SEH+0x75
fffff880`08d211c0 fffff880`04ca1e9c dxgkrnl!_real+0x2d8c
fffff880`08d211e8 fffff800`02cb984d nt!RtlpExecuteHandlerForException+0xd
fffff880`08d211f0 fffff960`003d187c win32k!gbUserInitialized <PERF> (win32k+0x2f187c)
fffff880`08d211f8 fffff960`003977cc win32k!_real+0x1fc
fffff880`08d21200 fffff960`000e0000 win32k!DereferenceW32Process <PERF> (win32k+0x0)
fffff880`08d21218 fffff800`02cb8625 nt!RtlDispatchException+0x415
fffff880`08d21220 fffff800`02ddf694 nt!_imp_NtOpenSymbolicLinkObject+0x918c
fffff880`08d21238 fffff800`02c19000 nt!KiSelectNextThread <PERF> (nt+0x0)
fffff880`08d21268 fffff800`02c19000 nt!KiSelectNextThread <PERF> (nt+0x0)
fffff880`08d21270 fffff800`02ddf694 nt!_imp_NtOpenSymbolicLinkObject+0x918c
fffff880`08d21288 fffff800`02e9db04 nt!BBTBuffer <PERF> (nt+0x284b04)
fffff880`08d212b0 fffff800`02c8ded3 nt!KiSystemServiceCopyEnd+0x13
fffff880`08d212b8 fffff800`02c19000 nt!KiSelectNextThread <PERF> (nt+0x0)
fffff880`08d212c0 fffff800`02e9db04 nt!BBTBuffer <PERF> (nt+0x284b04)
fffff880`08d212c8 fffff880`08d22ae0
fffff880`08d212e0 fffff800`02c8dac0 nt!KiSystemServiceHandler
fffff880`08d212e8 fffff800`02ddf694 nt!_imp_NtOpenSymbolicLinkObject+0x918c
fffff880`08d21328 fffff880`016629bb tcpip!TcpTcbReceive+0x50b
fffff880`08d21438 fffff880`01663e80 tcpip!TcpBeginTcbSend+0x670
fffff880`08d214d8 fffff880`01668d50 tcpip!TcpSendDatagramsComplete
fffff880`08d215a8 fffff880`016856da tcpip!TcpPeriodicTimeoutHandler+0x714
fffff880`08d21628 fffff880`016635f5 tcpip!TcpPreValidatedReceive+0x3e5
fffff880`08d21660 fffffa80`0a0fc010
fffff880`08d21668 fffff880`0163ec2a tcpip!IppPrevalidateLoopbackReceive+0x24a
fffff880`08d216b8 fffff880`01562d4b NETIO!FsbFree+0x6b
fffff880`08d216d0 fffff880`01772f90 tcpip!Ipv4Global+0x45f0
fffff880`08d216e8 fffff880`01772f90 tcpip!Ipv4Global+0x45f0
fffff880`08d216f0 00000000`00000000
fffff880`08d216f8 fffff880`0163e81e tcpip!IppLoopbackTransmit+0x2be
fffff880`08d21700 fffff880`0176e9a0 tcpip!Ipv4Global
fffff880`08d21798 fffff880`0176e9a0 tcpip!Ipv4Global
fffff880`08d217a0 fffffa80`0adde060
fffff880`08d217a8 fffff800`02c9a968 nt!KeExpandKernelStackAndCalloutEx+0xd8
fffff880`08d217b0 fffff880`0176e9a0 tcpip!Ipv4Global
fffff880`08d217d8 fffff800`02c8dc40 nt!KiSystemCall64
fffff880`08d217e0 fffff960`00271064 win32k!NtGdiDdDDISetAllocationPriority
fffff880`08d217e8 fffff880`0567b000 atikmdag
fffff880`08d217f0 fffff880`05d31b54 atikmdag+0x6b6b54
fffff880`08d217f8 fffff880`0567b000 atikmdag
fffff880`08d21800 fffff880`05d3252c atikmdag+0x6b752c
fffff880`08d21808 fffff880`0567b000 atikmdag
fffff880`08d21810 fffff880`05d22a64 atikmdag+0x6a7a64
fffff880`08d21818 fffff880`0413b000Unable to load image \SystemRoot\system32\DRIVERS\atikmpag.sys, Win32 error 0n2
*** WARNING: Unable to verify timestamp for atikmpag.sys
*** ERROR: Module load completed but symbols could not be loaded for atikmpag.sys
atikmpag
fffff880`08d21820 fffff880`041bc2f4 atikmpag+0x812f4
fffff880`08d21828 fffff880`04c85000 dxgkrnl!DXGADAPTER::AcquireDdiSync <PERF> (dxgkrnl+0x0)
fffff880`08d21830 fffff880`04ca6494 dxgkrnl!_fastflag <PERF> (dxgkrnl+0x21494)
fffff880`08d21838 fffff880`04c85000 dxgkrnl!DXGADAPTER::AcquireDdiSync <PERF> (dxgkrnl+0x0)
fffff880`08d21840 fffff880`04ca65cc dxgkrnl!_fastflag <PERF> (dxgkrnl+0x215cc)
fffff880`08d21848 fffff880`04c85000 dxgkrnl!DXGADAPTER::AcquireDdiSync <PERF> (dxgkrnl+0x0)
fffff880`08d21850 fffff880`04ca65b4 dxgkrnl!_fastflag <PERF> (dxgkrnl+0x215b4)
fffff880`08d21858 fffff880`04c85000 dxgkrnl!DXGADAPTER::AcquireDdiSync <PERF> (dxgkrnl+0x0)
fffff880`08d21860 fffff880`04ca65c0 dxgkrnl!_fastflag <PERF> (dxgkrnl+0x215c0)
fffff880`08d21868 fffff880`04c85000 dxgkrnl!DXGADAPTER::AcquireDdiSync <PERF> (dxgkrnl+0x0)
fffff880`08d21870 fffff880`04ca6614 dxgkrnl!_fastflag <PERF> (dxgkrnl+0x21614)
fffff880`08d21878 fffff880`04c85000 dxgkrnl!DXGADAPTER::AcquireDdiSync <PERF> (dxgkrnl+0x0)
fffff880`08d21880 fffff880`04ca6668 dxgkrnl!_fastflag <PERF> (dxgkrnl+0x21668)
fffff880`08d21888 fffff960`000e0000 win32k!DereferenceW32Process <PERF> (win32k+0x0)
fffff880`08d21890 fffff960`003d187c win32k!gbUserInitialized <PERF> (win32k+0x2f187c)
fffff880`08d21898 fffff800`02c19000 nt!KiSelectNextThread <PERF> (nt+0x0)
fffff880`08d218a0 fffff800`02e9db04 nt!BBTBuffer <PERF> (nt+0x284b04)
fffff880`08d218a8 fffff880`08d220d8
fffff880`08d218b0 fffff880`05725c9a atikmdag+0xaac9a
fffff880`08d218f8 fffff800`02cc95b1 nt!KiDispatchException+0x135
fffff880`08d21930 fffff880`0176e9a0 tcpip!Ipv4Global
fffff880`08d21938 fffff880`01661bd7 tcpip!IpNlpFastSendDatagram+0xb77
fffff880`08d21990 fffffa80`0a66d8c0
fffff880`08d21998 fffff800`02faa3c5 nt!MiUnmapViewOfSection+0x295
fffff880`08d219a0 0007ffff`ffffffff
fffff880`08d21a28 fffff880`05725c9a atikmdag+0xaac9a
fffff880`08d21a68 fffff880`01663e80 tcpip!TcpBeginTcbSend+0x670
fffff880`08d21a70 00000000`6d611261
fffff880`08d21c18 fffff880`04db3bf4 dxgmms1!VidSchiAllocateQueuePacket+0x158
fffff880`08d21c20 00000000`0000000c
fffff880`08d21c48 fffff880`04db3f09 dxgmms1!VidSchiAdjustWorkerThreadPriority+0x1c5
fffff880`08d21c50 fffffa80`07fcc010
Unplug any external devices if connected to your system.
Install the latest drivers for your video card. Sometimes drivers remain, not completely uninstalled. Follow this tutorial for complete removal of drivers of the particular program:
For monitoring the heat/celsius of the system, use Speccy or HWMonitor:
Video Card - Stress Test with Furmark
Monitor your temps with Speccy during this test

Warning
Video Card Stress Test with Furmark can damage GPU if temperatures are not taken care of.
Video memory test (for 20 passes)
Also peruse these links:
Quote:
When Furmark fails - there are still several possibilities.
- The most common ones -
- - Faulty Graphics Card
- - Underpowered/Faulty PSU (what is your PSU? Brand? Model?)
- - Faulty RAM (this is unlikely as you say the Prime95 Blend test and Memtest didn't show errors?)
- - Faulty Motherboard (unlikely - as it's been replaced)
- - Faulty CPU (very unlikely - anyway, Prime95 passed)
Reduce items at start-up. Nothing except anti-virus is required plus improves the time for logging in windows.
Disk Check on your hard drive for file system errors and bad sectors on it.
Let us know the results.