unusual shutdown

[decrepidoldman]

i am trying to help a friend with a comuter problem. the computer is an HP pavilion a818n with 2.93 gig pentium 4 515 prescot proccesor. the mother board is an asus PTDG1 LA.
this thing will shut down with out warning, like a complete loss of power, even after running only a few minutes or imediatly after start up. i have ruled out the power supply (tried a known good one) and the memory and memory slots. there is no error message and the hard drive is not the problem as i have installed a new one and it does the same thing. the only odd thing i know of so far is that the proccessor fan runs at full speed after the initial start up. it spins slowly at first but after the boot up, it revs. the fan started runninf fast all the time after the machune spent some time in a very hot apartment. if i clear the cmos by removeing the battery for 30 minutes, the problem goes away for a few days. i installed sandra lite on the hard drive and while there is no temerature reading on the main board, under proccessor, there is a temperature reading of 60 degrees c after the machine has been on for only about 1 hour. i am not sure if this is an actual temp or a limit as it seems high. i thought perhaps there is a bad temp sensor or the proccessor got fried, but the cmos thing makes me wonder. and if it is a censor, then is it in the processor, the fan, or the board? any ideas?
gary

[Raymond]

The bios should should have a temperature monitor. 60C is not very cool but the computer should survive under that temperature.

For a computer to shutdown without warning, it is usually the temperature or bad power supply. Memory usually causes auto restart and blue screens.

[stuge]

You should also run memory check utility .

[decrepidoldman]

the actual temp on the sisoft sandra lite report was 66 c and that was indicated to be the safe limit, not the operating temp. sorry. i ran the burn in program and it passed that fine, but there was a message that said no enviromental monitors found. i will check the bios.
gary

[decrepidoldman]

ran the burn in program again . there is no temerature or voltage imformation on the processor. i removed the processor and reseated and renewed the heat sink grease. when i started up again the rig shut down in the early stages of loading windows. repeated atempst to restart got worse and now it will shut off imeadiately.

[Raymond]

I guess you've narrowed down the problem to either CPU or mainboard. I remembered reading that after removing the battery for 30 minutes, the problem goes away for a few days... To me, it looked like the mainboard is failing.

You can try doing this as the last resort. Strip down everything and leave only the mainboard, CPU and memory connected. Unplug all power cables including the one that connects to the wall socket. Remove the battery from the mainboard for 30 minutes. Then press and hold the computer power button for 30 seconds to drain any power from the board.

Now put back the battery, and try booting only with the mainboard, cpu and memory. Perform a windows installation.