PC keeps turning self off

[Charmed]

During son3 morning ritual, he turns on pc, boots up fine, logs into his account fine. Gets up to grab breakfast, goes back pc is off.

Turn power off @ wall, then back on, boots up, goes to log in , pc turns off.

Again power off @ wall, back on, this process repeated several times, either you get to log into account or not.

Stuff it, I will just reformat, and it needed to doing anyway.
Reformat goes well, uninstall all the preloaded crap that was installed , dload & install, Avast Free Home, MSN, Yahoo Messenger & Firefox. Going out so turn off & continue later.

Get home & have to go through the above of turning off & back on at wall again. Unplug, take off panels, clean, check everything tight. Yep all ok.

Plug back in on & off a couple more times & finally able to log in.
Currently dloading & updating Windows.

System
XP Home ver 2002
(currently dloading & updating to Service Pack 3)

Aspire SA85 XPS MHD 12504 Intel
Celeron CPU 3.06 GHz
3.07 GHz, 224 MB of ram

So if any of the PC Nerds / Gurus have any idea what the problem could throw your thoughts this way.

Top of my list is either power supply or motherboard.

Sooner I can get on top of this the better, dont like sharing my laptop

[ricktas]

I have seen this with a loose RAM chip. Removing the RAM and re-inserting it resolved it. The other thing is over-heating of the CPU, if your PC has a temp sensor, it might be that the fan for the CPU isn't working, isnt working properly and the PC is shutting down due to CPU temp

[pgbphotographytas]

I have seen this be caused by a number of things.
First question is when did this start happening and was any new hardware added to the computer around the same time?

It would be worth unplugging all the internal power cables and replugging them to make sure they are tight, also check the RAM and all the drives to make sure they are plugged in and also check for any build up of dust or fluff inside the machine.

Paul

[Charmed]

Rick - Will check the loose RAM chip again in morning if prob continues. LOL to scared to turn it off right now, though did restart after the windows update & still running.

Oz - Power Management is ON

Paul - Started this morning & NO new hardware, and did the check dust,fluff, cables before. But as said above will do it again in morning if it still doesn't want to play ball.

[Tannin]

Check the CPU temperature first, if it isn't that, swap out the power supply. Power supply would be your #1 suspect. All the other suggestions are possible, but overheating (either of the CPU or (more likely) of a power supply component) is the most common cause.

[leanneqld]

My pc did that and it was the power supply. When it continually rebooted itself after a Bluescreen of death (BSOD) is was the RAM.

[Kym]

Power management on? Is is really off or just suspended?
Power options in Control Panel!