home built computer unexpectedly shuts down

[ebuckley]

I built a machine a couple of years ago. Always had a problem with the computer crashing. Symptoms were that the monitor screen would go black, the power light and HDD light would be lit on the tower, and the disk drive light (I believe it is the master drive not the slave) would be lit. It has been happening more recently, and isn't specific to a particular application. The only thing I can do when this happens is to shut off the power to the power supply and restart from there. The reset button doesn't work nor does holding down the power button for 4 sec's.
I should note that I'm an amateur builder. The machine is strong, even today...when it does work. Any thoughts would be greatly appreciated.
Thanks.

 

[dfuze]

Can you list your parts?

 

[ebuckley]

Pentium 4 3.4 GHz, ATI Radeon X700PRO, EPoX EP-5EPA MoBo, ASUS DVD ROM, NEC DVD Burner, WD Raptor WD740GD x 2, G.SKILL memory, Running Windows XP.
Cooling not a problem - at most this thing runs at 40C both system and processor.
Thanks for taking the time (anything I'm missing? Think I got all the major components

 

[dfuze]

You didn’t list your power supply.
Looking at your symptoms, I might lean toward a dying video card or power supply that isn’t supplying enough power. Out of those two, I think the most likely culprit is the power supply from your description. If it were the monitor, I would think by now it would have completely died. From your OP it sounds like the computer is up and running but just nothing on the screen. The light showing HD activity doesn’t care if it it’s the master or slave drive, just shows that it’s reading from one of the drives.

 

[KGB]

Examine the MB for bulging or burst capacitors.
It's about the right age.