New Build keeps freezing! HELP

[biggles]

Hi people, this is my first ever post so go easy on me!

Just built a new computer and it keeps freezing on me. I started off with XP Pro installation and it froze so I thought I would bite the bullet and get Vista, which I did installed it and still the same problem. I had the odd blue screen but that was driver problems with vista which is fair enough.
I have run windows update, check disk on the hard drive, mem test, checked the tmp (50-60 deg C), run virus scans. I reseated the GPU in another PCI-e slot and the RAM.

Running out of idea’s now can anyone help?

My PC Spec is:
MOBO - Asus P5NT-SLI
CPU - Intel Q6600 (artic freezer pro 7 HS)
RAM - Corsair Dominaotor DDR800
GPU - BGF Nvidia 8600 GTS OC
HDD - 2x 500Gb WD and 1x300Gb Seagate (which has windows on it)
NEC Lableflash DVD RW x2
OS - Vista Ultimate