Frustrating random shutdowns

[chunsa34]

Hi all,
we have a very frustrating random shutdown problem. My brother's computer would randomly shut down, regardless of whether he's playing games or leaving the computer idle. so it seems it's not a software problem.
Funny thing is it would shut down, but the green led light still blinks, and in order to turn it off completely he has to unplug the power cord and depress the power switch until the light goes off.
He suspected the power supply at first, so we got RMA replacement, and it happened again. Then we tried a different brand of power supply (thermaltake) and it still happened. so i took the computer to a computer repair shot, and the technician just tested the power supply, found it was defective, and sent me home. Well, I ordered yet another brand of power supply, and the problem's not going away!
My brother has also run memtest, reinstalled windows (after formatting the HD), and tweaked several power management settings. Still no clue with what's wrong with the computer. Please help!!!

 

[swker98]

Hi, deff sounds like a power supply problem, lets check to make sure that the psu that you have has enough juice to power your system

please most your system specs so we can help u better

 

[chunsa34]

It's not really a power-hungry system, at all.

The specs:

Amd Athlon 64 X2 4000+ 2.1 Ghz
1GB PC5300 DDR2 Ram
PNY geforce 7300 GT 256mb Graphics card
FSP group 400W PSU
Lite On 18X DVD writer
WD 80GB hard drive

 

[swker98]

how long will the comp shut off, is it any specific time or just random, also maybe the comp is overheating try to run it with the side off for a while and see if it still shuts down

edit: also make sure standby or hibrnate is off in windows but im prety sure its not that

 

[chunsa34]

i'm not sure what you mean by "how long will the comp shut off", but if you're asking how long it will remain shut off with green light blinking, then it remains that way indefinitely until i unplug the power cord.
it shuts off randomly. and it's not overheating, with CPU at around 35C at idle, 49-58 under full 100% Orthos load. The GPU is at 44C idle, 53 MAX while playing a game.
and yeah, standby/hibernate is off.

 

[swker98]

it sounds like maybe a motherboard problem or video card since you said you changed your power supply. does the computer have onboard vid if so try it out and if you have a spare vid card around to try that wouldn't hurt, jsut try to rule out some things that it could be. also check the motherboard for any bulging or leaking compactors (google bludged compactors if you dont know what this is)

Is your comp plugged into a surge protector, if so try to plug it into the wall for a little while and see if it works. also it woundent hurt to try another power cord but i dont think thats the problem.