I recently obtained a used P35-609. The problem im having is getting it to power up and stay on longet than 5 seconds. Oddly if I enter into BIOS at power on it will remain on. Thus far iv left it on for 20 min. Iv tried removing reseating devices, no luck and no change. Hopefully someone has ran into this problem or at least heard of it and conquered it.
Any and all help is greatly appreciated.[

That usually indicates a dead componet, Have you tried removing everything except the CPU from the mobo? if it will stay up you can add componets back until you find the one that kills it. If it still has problems when everything is removed then your mobo is bad.

is the heatsink seated properly to the CPU? stupid question but its been done, i had one doing it for a while couldnt figure it out it would run for about 10 min or so trying to install windows then it would shut down as soon as the load put a little bit of a strain on it, then it would shut down from overheating. it would enter bios just fine and everything and it would be fine but when you stressed it a bit off it went. just a place to check thats simple.

Sorry it took so long to post. I did remove the heat sink, cleaned it, apllied new heatsink and nodda.. same problem continues. Thanx for your efforts all but im giving up on this one and resigning to a MB prob. At 200.00 a pop its safe to say iv sold it for parts..

I had the same problem, i just replaced the power supply and it worked like a charm.