System shuts down during gameplay.

Two years ago I built my computer according to the recommendations made by a friend of mine. The items of interest were:

-MSI P67A-GD65 (B3) LGA 1155 Intel P67 SATA 6Gb/s USB 3.0 ATX Intel Motherboard

-GIGABYTE GV-N460OC-1GI GeForce GTX 460 (Fermi) 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card (Two of them)

-CORSAIR Vengeance 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model CMZ8GX3M2A1600C9B (Two of them)

-Intel Core i5-2500K Sandy Bridge 3.3GHz (3.7GHz Turbo Boost) LGA 1155 95W Quad-Core Desktop Processor Intel HD Graphics 3000 BX80623I52500K

-Rosewill BRONZE Series RBR1000-M 1000W Continuous@40°C, 80Plus Bronze Certified,Modular Cable Design,ATX12V v2.3/ EPS12V,SLI Ready,CrossFire Ready,Active PFC"Compatible with Core i7, i5" Power Supply

It worked well and I was able to play everything including Bioshock Infinite on high settings until a few months ago. After that my computer would shut down in the middle of game play. I thought it was related to overheating until it happened after my computer had only been on for like five minutes and HWMonitor didn't show any high temps anywhere.

I thought it may have been the graphics card so today I went out and bought a Geforce GTX 760 by EVGA and it happened again. I have front, top, and rear fans on high and the card has its own fans.

What's the problem?

Some DxDiag stuff for good measure...

Time of this report: 9/29/2013, 13:05:29
Machine name: QUENTIN
Operating System: Windows 7 Home Premium 64-bit (6.1, Build 7601) Service Pack 1 (7601.win7sp1_gdr.130801-1533)
Language: English (Regional Setting: English)
System Manufacturer: MSI
System Model: MS-7681
BIOS: BIOS Date: 03/02/11 10:58:35 Ver: 04.06.04
Processor: Intel(R) Core(TM) i5-2500K CPU @ 3.30GHz (4 CPUs), ~3.3GHz
Memory: 8192MB RAM
Available OS Memory: 8172MB RAM
Page File: 2221MB used, 14121MB available
Windows Dir: C:\Windows
DirectX Version: DirectX 11
DX Setup Parameters: Not found
User DPI Setting: Using System DPI
System DPI Setting: 96 DPI (100 percent)
DWM DPI Scaling: Disabled
DxDiag Version: 6.01.7601.17514 64bit Unicode
--------------------------------------------------------------------
Card name: NVIDIA GeForce GTX 760
Manufacturer: NVIDIA
Chip type: GeForce GTX 760
DAC type: Integrated RAMDAC
Device Key: Enum\PCI\VEN_10DE&DEV_1187&SUBSYS_37693842&REV_A1
Display Memory: 4038 MB
Dedicated Memory: 1990 MB
Shared Memory: 2048 MB
Current Mode: 1920 x 1080 (32 bit) (60Hz)
Monitor Name: Generic PnP Monitor
Monitor Model: SMS23A550H
Monitor Id: SAM07C9
Native Mode: 1920 x 1080(p) (60.000Hz)
Output Type: HD15
Driver Name: nvd3dumx.dll,nvwgf2umx.dll,nvwgf2umx.dll,nvd3dum,nvwgf2um,nvwgf2um
Driver File Version: 9.18.0013.2723 (English)
Driver Version: 9.18.13.2723
DDI Version: 11
Driver Model: WDDM 1.1
Driver Attributes: Final Retail
Driver Date/Size: 9/17/2013 22:22:42, 15703688 bytes
WHQL Logo'd: Yes
WHQL Date Stamp:
Device Identifier: {D7B71E3E-52C7-11CF-5151-64171CC2C435}
Vendor ID: 0x10DE
Device ID: 0x1187
SubSys ID: 0x37693842
Revision ID: 0x00A1