Random Reboots

Just installed a new motherboard Gigabyte(GA-P35-DS3L), Windows install went fine, but I keep having random reboots, at first I thought it was when I ran coretemp.exe, but I just recently got another random reboot just idling on a webpage. Any ideas? pretty sure its not hardware related as it never done it during the windows install.

e6300/gigabyte-DS3L/2gbcorsair5300/gigabyte6600GT/480w purepower

Nismo

Only sites i've visted:
nvidia.com
google.co.uk
firefox.com
here
winrar.com
So pretty much rules out a virus/spyware

What voltage are you running the RAM at? If at normal then try upping the voltage a notch.

1.8v

edit - been up for awhile now, strange