Okay, i just finished building a system and now its unstable. Symptoms have been very intermittent. On first boot it started up okay and ran for a couple hours (enough time to install windows and drivers). About 5-10 minutes after installing Intel desktop utilities the system shut itself off. I noticed before it shut off that the +3.3v voltage was kind of low in the hardware monitor.
So after it shut off it wouldn't boot, the fans would turn on for a split second, and then nothing. I unplugged everything except the motherboard from the power supply, the fans turned on for a little bit longer, then nothing. After messing around with it some (Unplugging various things and turning it back on again a few times) it booted up again. and i'm using it now without the front usb/firewire/audio plugged into the board.
So of course now it boots, but it'll only stay on for a while, and if I run anything remotely taxing (Half life 2) it hangs.
I feel like this could be a power supply issue because of the not booting, but i'm no expert.. I feel like it might be the motherboard because of intel's stupid Quiet Cool Technology or whatever, my fans run at below 1000rpm. Any help is greatly appreciated. Here are the specs:
ATI Radeon x1950xt
2gb GSkill dual channel
Intel DP965LT motherboard (i'm worried this or the power supply is the culprit)
Seagate 320gb SATA HDD
CDRW/DVD combo drive
Antec Smartpower 2.0 500 Watt PSU (17 amps on the first +12v rail and 19 amps on the second +12v rail)
Assuming power is the problem, i bought and tried a 750-watt thermaltake toughpower PSU (4 12v rails at 18 amps each).
Tried half-life 2, lost coast at 1280x1024. Ran fine for about 3-5 minutes and then did its usual thing of hanging. Note that it doesn't actually shut off completely, the power light stays on but the screen doesn't show anything.
Did you update your GPU drivers. Bad drivers can certainly cause system hangs. Sometimes it is simply your combination of componenets that a driver may not like. Try the latest one most likely different from what you card shipped with as they seem to be ever evolving.