I have 2 old computers setting around the house that I was going donate to my Local Union for the appretice to use at school. One of them I got up and running and the other won't stay powered up for me. It is a HP Pavilion XE734 with a Celaron 600MHZ CPU, 128mb of ram,15gb hardrive, and integrated graghics. Now, when I plug in the power cord it powers up by itself ( without pushing the botton). And it will run for 5 seconds and then power down. I blew it out good. Thats about all I did to it. I don't want to throw it away if someone can get some use out of it. Any response will be apppreciated.

have you tried clearing the cmos? sometimes reseating ram sticks and cards help too when booting a computer thats been off for a while.

Sounds lke the power button is stuck or flipped around the other way...

That's a possibility. Try disconnecting the power switch connector from the mobo. Short the pins with a screwdriver or something to turn it on.

I would try removing the expansion cards first, like the modem and what not and see if that helps.