No BSOD but system keeps on randomly shutting down

[Britton30]

The dump had the same fault as before. Is the machine overheating, clogged with dirt, fans stopped running?

Does this company have an IT department?

 

[MrCube28]

Everything is new, fans are working fine. I haven't checked the core/system temp while the computer is running but I have switched it back on straight away when it goes off and checked in the BIOS and the temp is usually 20-21C (about 68F).

The guy who owns the computer is self-employed and works alone, no employees.

 

[Britton30]

Did you post the make/model of the PSU?
If it will stay on long enough download these to check temps while running.
Downloads | techPowerUp For CPU

Downloads | techPowerUp ForGPU

A shot in the dark. Is the cables/plugs from the wall all in good order and not working loose? If it's on a UPS, is the battery up to date?

EDIT: I've been told the +VCC +D -D and GND connectors may be for a USB header.

 

[Slartybart]

The machine just shuts down, it doesn't restart - is that correct?

Does it exhibit this behavior in safe mode (minimal)?

A few random musings:
Nvidia driver
Supported products - GeForce 7 series: 7950 GX2, 7950 GT, 7900 GTX, 7900 GT/GTO, 7900 GS, 7800 SLI, 7800 GTX, 7800 GT, 7800 GS, 7650 GS, 7600 LE, 7600 GT, 7600 GS, 7550 LE, 7500 LE, 7350 LE, 7300 SE / 7200 GS, 7300 LE, 7300 GT, 7300 GS, 7150 / NVIDIA nForce 630i, 7100 GS, 7100 / NVIDIA nForce 630i, 7100 / NVIDIA nForce 620i, 7050 PV / NVIDIA nForce 630a, 7050 / NVIDIA nForce 630i, 7050 / NVIDIA nForce 610i, 7025 / NVIDIA nForce 630a

Edits:
More information on RAM, please. G-Skill perhaps?

Any visible damage on the mobo - blown capacitor ?

Nvidia system tools
--> Documentation (PDF)

General information you probably already tried, but

There was more, but it takes me a while to find things and post.
PS: that's about the cleanest inside of a PC I've ever seen =:>

Bill
.

 

[Dave76]

Usual suspects are RAM and PSU.
New doesn't mean it's not faulty.
Your link to the motherboard manual is in Chinese, kinda hard to read.

Did you test the system with your PSU?

Run memtest86+ for seven full passes (when pass 8 starts you can stop it), this may take several hours so best to run overnight.
If you get any errors you can stop the test.