New PC Frequent Crashes

I have a new PC, just 3 days since delivery that crashes all the time. Spec is below. The crashes can happen at any time, even at the log in screen. However, at times it has run for over an hour without crashing. At no time is a BSOD or any error message produced.
The supplier support has asked me to increase the CPU VCORE TO 1.25v which I have done. Still it crashes.
I have gradually installed all Windows updates that I can in between the failures. There are 10 updates that fail with a Code 80073712 error. I have tried to correct this by running DISM.exe but often a crash occurs when this is running.
Be really grateful for any guidance. I've been at this for nearly 3 days and am exhausted!

Spec is:
CPU: Intel(R) Core(TM) i5-3470 Quad Core 3.20 GHz 6MB Cache LGA1155 + HD Graphics
FAN: Intel Socket LGA 1155 Standard CPU Cooler [-23]
HDD: 2TB SATA-III 6.0Gb/s 64M Cache 7200RPM Hard Drive [+13] (Single Hard Drive)
MEMORY: 8GB (2x4GB) PC12800 DDR3/1600mhz Dual Channel Memory (Kingston HyperX Blu w/Heat Spreader)
MOTHERBOARD: Gigabyte GA-Z77-D3H Intel Z77 Chipset, ATX Mainboard w/ 4 RAM slot, IRST, Lucid Virtu MVP, Ultra Durable4 Classic, 7.1 HD Audio, GbLAN, 1 x Gen3 PCIe x16, 3x PCIe x1 & 1 PCI ***Overclockable XXX*** [+34]
NETWORK: ONBOARD 10/100/1000 GIGABIT LAN PORT -- As standard on all PCs
OS: Microsoft(R) Windows 8 (64-bit Edition) (64-bit Edition)
POWERSUPPLY: 500 Watts Power Supplies (CoolerMaster Elite 500watt Gaming Power Supply)
SOUND: HIGH DEFINITION ON-BOARD 7.1 AUDIO
USB1: Built-in USB 2.0 Ports
VIDEO: AMD Radeon HD 7750 2GB 16X PCIe 3.0 Video Card

Don't think the updates would help. But, getting them to install is a separate problem. If your crash problem cannot be solved by the supplier, then I would return it. Maybe you'd want to try another of the same model, but, then, maybe not.

To take a stab, you could try turning fast startup/hybrid shutdown off. Fast Startup - Turn On or Off in Windows 8

What BSOD says ??? is there any errors in the event viewer, that might be related to your crashes ?