Odd reboot issue

12 May 2005
Cambridge, or somewhere else in the world
Hi guys,
hopefully someone can shed some light on this issue I've been having.

I am having a reboot issue that is repeatable every time I boot from cold.

The pc gets to the Windows 8 login screen, sometimes I can type in my password, usually I get to the desktop or whatever the icon page is called and the pc reboots. Once its rebooted a second time - it's rock solid. It's probably something really simple...

And I've checked and rechecked my connections to the motherboard, but still doing it....

anyhow, specs:

Intel i7-3770K
Asus P8Z77-V LX
Samsung Green 16 GB (4x4GB) DDR3 PC3-12800C11 1600MHz 30nm Dual channel kit
Nvidia 460GTX
Samsung 830 Series 256GB SDD for OS
Win 8 beta
Corsair TX750M PSU
several other HDD for data etc.

If you can shed any light to fix this, this would be great.