Strange shut down

[Batwing]

I have a friend who has a computer with an ASUS motherboard and an nVidia videocard. That is as specific as I know right now. I can dig into her machine later.
However, here's the problem. The monitor will shut down for no reason. The computer continues to run. The monitor does not go to sleep, but the computer has to be rebooted for the display to come back on.
She has changed video cards.
I am leaning toward a motherboard problem, except for it coming right back on with a reboot.
Any ideas?
Thanks

 

[GamesMasta]

Try monitor on a computer that doesn't have that problem. That way you can figure out whether its the monitor or the system.

Also, when does the monitor tend to shut off: randomly, or at distinct events.

 

[Batwing]

We swapped monitors while it was doing this. No good.

 

[mechBgon]

Maybe the power supply is a bit overloaded. The power supply's "effective payload" goes down as it gets hotter, so you might ask your friend if the computer is out in the open where it can get cool air. Don't want it closed up in a computer hutch or something.

A power supply that is marginal may do that regardless, so if you can get the precise brand/model of PSU, we can gauge its general reputation for quality and what sort of hardware load it would be suited to.

 

[Batwing]

Here are the specs -
Motherboard is a Gigabyte GA-7ZXE
videocard is ATI Radeon X300SE with 128 DDR Ram
300 watt power supply.

If the power supply is not large enough - could this couse the videocard to shut off and leave the rest of the system running?

My only ooption after the power supply is the motherboard itself.