Frequent BSOD -

No firm answers from the BSOD's, although they are suggestive of issues with your video card/drivers.

Try running this free video stress test: FurMark: Graphics Card Stability and Stress Test, OpenGL Benchmark and GPU Temperature | oZone3D.Net
Try downloading the latest video drivers from Drivers - Download NVIDIA Drivers
- then uninstall the current video drivers and install the freshly downloaded one's.

Open up the case and ensure that the video card is properly ventilated (and the fan works) and that all the power plugs are tight.

If you have a spare video card, try that in place of the current one (to see if it's a problem with the card).

Post back with further memory dumps if this doesn't fix it.

Summary of the memory dumps:

Code:

BugCheck 3B, {c0000005, 1, fffff88007393b70, 0}
Probably caused by : ntkrnlmp.exe ( nt!KiSystemServiceHandler+7c )
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BugCheck 50, {fffff87ff5f406a8, 0, fffff88003f2cd28, 5}
Probably caused by : afd.sys ( afd!RtlCopyMdlToBuffer+0 )
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BugCheck 50, {fffffa806ed46410, 1, fffff8800439c10b, 5}
Probably caused by : hardware ( dxgmms1!VidSchiWaitForSchedulerEvents+4b )
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BugCheck 1000007E, {ffffffffc0000005, fffff88010b37314, fffff880056d8668, fffff880056d7ec0}
Probably caused by : dxgmms1.sys ( dxgmms1!VIDMM_GLOBAL::EndPreparation+ec )
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BugCheck 50, {ffffffff8570245d, 1, fffff8800ff40d0d, 5}
Probably caused by : nvlddmkm.sys ( nvlddmkm+d2d0d )