Problem with power, please help

[atvking]

My friends computer has been having a problem recently with staying on. When you start the computer it will run almost until xp boots, then shut off, then reboot itself, then it runs for a shorter time, then this process repeats until it doesn't even post. If you let it sit awhile it will boot in xp again, then repeat the same process again. I went into the bios and the cpu temp seemed fine, around 45c (if that has anything to do with it), I also checked the voltages and got 12.249, 5.145, 3.280, 1.344. I am unaware of all the specific hardware, but I know it runs a core 2 quad, asus mobo, 4gb ram, onboard video. I have noticed a high pitched whine coming from the psu when the computers off, and the psu is some old generic 500w. They also left their computer running ALL the time. I think it might be a warn out psu, but I'm not entirely sure. If you have any ideas please let me know
Thanks.

 

[trents]

Sounds like it would either be a bad motherboard or a bad PSU and with the info about the high-piched wining noise it sounds like the PSU. Probably a bad capacitor whistling. If you have a spare PSU or can at least temporarily rob one off another system you can check that out.

 

[atvking]

It was the PSU, I have installed a new 500w 80 plus cert. PSU and everythings working fine. Thanks for the help.