By randomly rebooting do you mean it boots into windows completely then randomly reboots or you switch on, it lights up then goes off and then reboots completely?

 

Hrm, could be a number of things, how frequent are the reboots? If it's stable for an hour or so you could try running Prime 95 for a bit to test cpu stability.

 

It sounds like a instability problem.

I take it that because it's a new build you have not OC anything yet? The only thing I can suggest is that you start up.. go to bios and carefully check through all the settings again. Tedious I know but sometimes a duff defaut setting on that ASUS board will make it fail to boot or reboot if the MB detects a problem. I had the same with my P5Q recently. I only changed one setting and the silly thing would go round in circles until I acknowledged the post message that it was failing to boot.

Doubt if it's a PSU problem because 650watts, which is a good supply for that setup.

 

I think the PSU might be overloading. I've had a similar thing with one of my builds in the past. Try to reconnect things so that you don't have your hard drive connected on a lead that also connects to other things. Try to use as many leads as possible from your PC to connect stuff up.

If your PSU has one cable per connection, though, it might be something else.

 

That's interesting... Keep us updated.