Pc shutting itself down

[brooks25]

im not sure if this is the right place to post this but it seems to involve the motherboard but im not sure..
i built a computer about 2-3 years back and always had some problems with it, powering down randomly and not turning on unless i open up the case and jiggle the wires, stuff like that. recently my gpu seemed to die, anytime id play a game the color would distort and it would freeze up, so i ordered 2 new cards to try some sli, i had a gefore 8800 or some such in there and upgraded to 2 geforce 9800 gt. they showed up today and when i try to put em in the computer and turn it on itll start up and run for about 15 to 20 seconds then just turn itself off, i tried it with one card, the old card, moving the cables around, and whatever else i could think of and it does the same thing every time, runs for about 15 to 20 seconds then powers down, and if i try to immediately power it back up itll only run for about 2 seconds before shutting down, it shuts down in the bios and the first time it seems to shut down when i try to run it in default settings, i get enough time to load default and try to start it then itll die... the only thing i can think of is in my stupidity when i built it i did not screw in the ground wire on my psu and just kinda left it sitting around in the cast, not touching any components but stull not secured because i had never seen a ground wire in any other psu ive installed on other machines ive built, so im not sure if my psu is bad or if my mobo has started failing from power surges and im not sure what else to do to check before i buy more components
i use an asus p5n-d mobo and an abslab tagan bz800 psu
any ideas what could be the problem or how i could test? i dont have a multimeter atm but might need to pick one up

 

[T_T]

The best way to test your PSU w/o a multimeter or anything of that nature, is to test it as you increase its workload. To start, remove everything from the motherboard, except for the CPU and Heatsink/Fan.

Turn on the power to your computer. Does it still shut down right away? If so, then you may need to replace the PSU or the mobo battery. If not, continue to add on one device at a time (including RAM-one stick at a time).

While 800w is a hefty output, you should be more concerned with how much load each +12v rail can handle. W/o a multimeter or PSU bench tester, you are limited to load testing. Find out how much stress your PSU can take before shutting down.

 

[TheEphraim]

I would agree with T_T.

 

[NuclearShadow]

I'm honestly confused onto why you would continue to use the PSU for such a long period of time knowing its likely faulty. You could really do harm to your other hardware.

While T_T gives good advice I personally wouldn't bother nor add anymore risk to the hardware. You should have returned that PSU once you begun to have the problems. So just pick yourself up a new one you clearly need a new one anyways even if you have done damage to any other hardware. But there is no way to safely tell without a new PSU.