Shutdown while Gaming

[JPv]

Ey guys. I just finished building first desktop in my life, everything went well until I tried out playing games. at random times, the computer shuts down. Samething with when I did bench mark with FurMark, it shuts down at beginning usually (the farthest i've gone was when the temperature hit around 55-60). Also, sometimes when I leave the computer on, and it is turned off, and I know that happened not because of the power save mode (which I dont even have it on), but it caused by something else as I see the message that says the computer was not turned off properly.
I'm assuming it's either PSU problem or the temperature of one or more of the hardware, but I'm not sure which one is the problem. I hope somebody can bring me solution ASAP, I'd appreciate for your help!

Here's my Spec:

OS - Windows 7 Home Premium 64 bit

CPU - AMD Athlon II X4 640 Propus 3.0GHz Socket AM3 95W Quad-Core Desktop Processor

CPU Fan - ZALMAN CNPS9900ALED 120mm 2 Ball Low-noise Blue LED CPU Cooler

PSU - Rosewill Xtreme Series RX850-S-B 850W Continuous @40°C ,80 PLUS Certified, ATX12V v2.2 & EPS12V v2.91, SLI Ready

HDD - Western Digital Caviar Blue WD6400AAKS 640GB 7200 RPM SATA 3.0Gb/s Internal Hard Drive

Ram - G.SKILL Ripjaws Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL9D-4GBRL

Mobo - Asus M4N98TD EVO - Socket AM3, NForce 980a SLI, ATX, RAID, SATA, Gbit LAN, Hybrid SLI

GPU - EVGA 768-P3-1360-TR GeForce GTX 460 (Fermi) 768MB 192-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card

CD/DVD ROM - ASUS DRW-24B1ST/BLK/B/AS Black SATA 24X DVD Burner - Bulk - OEM

Sound Card - Creative 70SB088000004 7.1 Channels PCI Express 1x Interface PCI Express Sound Blaster X-Fi Titanium

Case - Antec Nin Hundred Two

Average Temperature without gaming:

(From SpeedFan 4.41)
GPU: 30c
Temp1: 26c
Temp2: 27c
Temp3: -128c (?)
Core: 12c

 

[joh06937]

definitely sounds like either a psu problem or a heat problem, although it could maybe be instability. are they bsods? are you overclocking anything? if so, what component and at what settings?

for the heat possibility, try running prime95:
http://files.extremeoverclocking.com/file.php?f=103
watch the temps (cpu) for that one and see what they max out at. prime95 will also fail (and most likely cause a bsod) if your cpu is unstable.

also, run furmark and see what temps your gpu gets to.

it is possible that it could be your psu but since yours is 850w i would be surprised if that were it.