I Turn PC On - 5 seconds later it turns off - Please Help!!

I built a new PC about 3 months ago. Last week I turned it on and 5 seconds
later it turned off. No beeps, no memory check, etc. I dicconected both of
my DVD burners and both of my hard drives and it still didn't work so I know
that I wasn't pulling more power than my PS could handle (not that I am even
close to pulling 420 watts with my other hardware. I figured it was the
power supply (420W) that came with my new case. So I installed a new Antec
500W power supply and the same problem. After the 4th attempt the PC booted
and ran for 48 hrs. I came home today and PC was off. PC was running fine
for 3 months and all the temperatures were correct throughout that time so I
know I didn't burn out the CPU. I can only assume that it is a defective
motherboard but don't want to rush out and buy another to find out (if I do
that I may as well start building a 4th computer) since I am still under
warranty and will get a replacement motherboard as a result. If anyone can
enlighten me if they have had a similar problem or know what my next step
should be I would be deeply appreciative. Much thanks, Tom.

Sounds like a defective motherboard indeed. It must be such a drag. I
hate it when new motherboards don't work.

Do you mind telling me which motherboard it is? And what about the rest
of your system specs? Sometimes it is due to a unique combination of
hardware and software that causes this type of problems.

Best Regards,
Gary Hendricks
http://www.build-your-own-computers.com

Gigabyte GA-8IPE1000 Pro, P4 3.0ghz 800mhz 1mb cache, 2 x 512mb PC3200
400mhz RAM, 256mb EVGA Nvidia 6200 8x AGP Video, Maxtor 40gb system drive
(master), Maxtor 120gb data drive (slave), Lite-On LDW-411S -R -RW +R +RW
DVD Burner (master), Panasonic LF-D521 DVD -R -RW RAM Burner (slave),
Windows XP Pro SP2 / Windows 98, Norton Internet Security 2005, Partition
Magic 8, MS-Office 2003. Original InWin 420w Power Supply (included w/ case)
replaced w/ Antec 500w SP500.

"Gary Hendricks" wrote in message
oups.com...
Sounds like a defective motherboard indeed. It must be such a drag. I
hate it when new motherboards don't work.

Do you mind telling me which motherboard it is? And what about the rest
of your system specs? Sometimes it is due to a unique combination of
hardware and software that causes this type of problems.

Best Regards,
Gary Hendricks
http://www.build-your-own-computers.com

Check your case's power button... is it jammed?

Check the sittings of the motherboard sometimes it also causes a lot of
problems. Unscrew the mobo from the casing and resit it. This is caused
due to vibrations and heat changes.

Hope it works. ...

Check the sittings of the motherboard sometimes it also causes a lot of
problems. Unscrew the mobo from the casing and resit it. This is caused
due to vibrations and heat changes.

Hope it works. ...

Tomwrote:
I built a new PC about 3 months ago. Last week I turned it on and 5
seconds
later it turned off. No beeps, no memory check, etc. I dicconected
both of
my DVD burners and both of my hard drives and it still didn't work
so I know
that I wasn't pulling more power than my PS could handle (not that I
am even
close to pulling 420 watts with my other hardware. I figured it was
the
power supply (420W) that came with my new case. So I installed a new
Antec
500W power supply and the same problem. After the 4th attempt the PC
booted
and ran for 48 hrs. I came home today and PC was off. PC was running
fine
for 3 months and all the temperatures were correct throughout that
time so I
know I didn't burn out the CPU. I can only assume that it is a
defective
motherboard but don't want to rush out and buy another to find out
(if I do
that I may as well start building a 4th computer) since I am still
under
warranty and will get a replacement motherboard as a result. If
anyone can
enlighten me if they have had a similar problem or know what my next
step
should be I would be deeply appreciative. Much thanks, Tom.

Before you trash the mobo, try putting in a new c-mos battery. When
they go dead, sometimes they'll do strange things as this. I've had
a whole host of problems with dead batteries that don't make sense.

While most will only force you to reset the clock, some will cause
havoc. Either way, it zeros the bios.

All will have to find your processor again and go through the whole
setup ritual. Some do this better then others. Some still, may
default to a test setup that doesn't exist. I've had Compaq's do
this.

My Lan Party board cuts the FSB speed in half by default. It finds my
processor and runs the RAM bus at half speed. You have to set it
manually. You actually have to "overclock" it, to get it to run at
the chips default speed. That's really strange.

This sounds like it's the case, as all things being equal, it ran fine
before. All things are equal, right?

And remember, any custom bios settings you might have had will be
gone. It could be something as simple as a default change back to a
boot device that isn't there. Couple that with a shut down setting
on error, and it could very well be as simple as that.

I also had a battery go dead in about that time frame on a new board.
Worth spending the 4 bucks.

Another quick check is to make sure you physical power button isn't
stuck in. Cheap cases are known for this, but it could happen to
any. Holding the switch in too long will cause a power down if your
power settings are set that way. Most defaults are set to that.
They all have two settings, one to hybernate the machine, and one to
shut it down.

Best of luck