PC powers off under load

Built a system from old and new parts. This has been a disaster from square one. Originally had a Gigabyte P45 board that was faulty. System would never stay on for more than 2 minutes in BIOS, with only CPU, Mem and Vid card. Tried every possible scenario, different memory, different power supply the works, that MB was not working. So RMA'ed it and got the Asus board.

Now have had some issues as well with this system, but its at least up and running. Was extremely unstable with 2 sticks of memory and so far seems OK with 1 stick if I don't do any loads on the system. All the other issues to this point I hope is moot and won't bring them up unless needed.

If I run a game Team Fortress 2 or Left4Dead system powers off after a few minutes. Check temps on Processor and Vid card, not overheating. Checked in BIOS checked in windows. Have tested each mem stick individually using memtest86, they each passed. I tried is once using both sticks and PC powered off after maybe a minute, didn't try both sticks again.

Ran chkdsk on both drives, no errors. Decided to download SiSandra and run a CPU load, this resulted in the PC powering off after 30-60 secs. So can rule out the video card. Could this rule out powersupply as well?

Now would any of this indicate an actual problem device? Like is this definitely the CPU or the Memory or the Power Supply, maybe the Motherboard? I want to fix this and get a stable system I can use, but am running out of ideas here.

Can anyone suggest other tests or troubleshooting? The only real common parts from first failed MB is the processor and power supply. People tell me that CPUs very rarely are faulty. And this powersupply was working fine in the Athlon 64x2 system running just prior to this build.

All ears at this stage, thanks in advance.


System Specs New Equipment
Asus P5Q Pro Motherboard
G.Skill DDR2 800 (2x2GB)
or
Patriot Viper DDR2 800 (2x2GB)
But currently running only 1 stick and been trying each brand.
Intel Core Duo E8500
Liteon DVD

System Specs Existing Equipment
FSP 600 Watt Power supply
Evga GeForce 8800GT
WD Raptor (boot drive)
WD Caviar

XP Pro SP3

 

Hi m8, I have just built a system, not so different to yours, except I have the 9800Gt and only one hard drive.

I had a 500w PSU in it to start with and it would do the same thing.

So I upgraded to a 650w and that sorted it.

I'm not saying it is the same thing, but you could buy a new 700w PSU try it out and if it dont work then take it back.

 

One thing to try is take the connector for the video card out and use the other one. On the specs it says rail 2(of 4) is cpu/pcie 2 while rail 4 is pcie1 .Kind of a long shot but worth a try because if your cpu and video are on the same rail they may be overloading that rail. The psu you used to test on the previous board, was it larger then your current psu?

 

The 600Watt power supply was from my previous system. It was working fine in that system. Only difference with the new build is the CPU/Mem/MB

I had done a CPU benchmarking test and that made the system crash as well, so its not really doing anything to the vid card, so thats a lot of extra power that is not being used for that test. I can't see the power supply being the issue.

Anyway I tried the Patriot Memory, used just 1 stick and system was way more solid. I was able to play some games for over 30 minutes. Tried later with both sticks in and PC crashed. So something with the memory and MB seems to be the culprit.

Could this just be Voltage settings with the MB? I had found some posts on another forum recommending voltage and timing settings for this memory. SO think I will try that next.

Also memory passes tests in memtest86 boot cd, so not sure if that means its more of an issue with how windows is using/accessing the memory?

Very frustrating to say the least, but I seem to be making progress slowly and getting more stable the more I do.