computer starts then shuts down after 10-12 sec

I have a 12 year old home built computer running winXP sp3 and a 1+0 Adaptec software RAID. Replaced Power supply with PC Cooling unit a couple of years ago. Have replaced several of the Seagate Cheetah drives as the machine runs 24x7. The other day the computer started up and shut down in 10-12 sec before I can enter the BIOS and without any beeps. I tok out and replaced the battery to reset the CMOS. I can't find any obvious shorts. I doubt the power supply has gone bad, but I do have a tester, just haven't done it yet. Other suggestions? Thanks.

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rwalker1Author Commented:
Would a POST test card be helpful?
Any suggestions as to a specific card?
dbruntonQuid, Me Anxius Sum?  Illegitimi non carborundum.Commented:
Disconnect all external peripherals, network cable, mouse, keyboard, printer, USB etc
Disconnect all hard drives, floppy drives, CDROM drives and any other internal drives etc.

Try the reboot and see what happens.  It should start and hang on the BIOS screen if all is OK.

No joy then check heatsink and fan properly attached and fan works when you turn on power.

Report back results.

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The RAM is bad.
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what motherboard model is this?
a machine from that era may suffer from bad capacitors - so check  the mobo for bulging - leaking ones:   c
Danny ChildIT ManagerCommented:
If you've done as dbrunton suggests, and done a barebones boot and left it there for a bit, you'll have a system with a moderately functioning motherboard, RAM, CPU and fan.  Even leaving it at the BIOS level is a test of sorts.  

After that, I'd reconnect the dvd drive (only), and boot from a Knoppix or Linux disk, just to increase the load a bit.

If that works OK, I'd power off, connect the hard disk, boot again, but into Knoppix again, and see if the hard disk is working.  If it's visible, might be a good time to copy off any essential files/photos/mails/music/docs, etc - assuming you don't have a good backup elsewhere.  

Once this is done, try to boot from the hard disk again, perhaps into Safe Mode, perhaps with a Repair Install, and see how that goes.

Normally, brutal full shutdowns as you describe are hardware related (and often heat-related), so working through the steps above might show which one it is.  Double check the CPU fan, and perhaps dust it down with an airduster.  

If still bad, before you go much further, connect the hard disk as a slave in another system or in an external USB disk cage and ensure that all key data is backed up, and visible.
and of course - verify that all fans run fine, and clean the system from dust
Highly likely the video card is also going bad.
If the system starts and then suddenly dies like my spare system it was the video card.
I replaced the ram and cleaned everything for dust checked the mobo for swollen capacitors  in the end it was the video card.
RojoshoRTCC-III Level-2 SupportCommented:
Hello rwalker1,

Sorry for being late to the party.

All of the above suggestions are GREAT.  I will take a different position - I think.
With a 10-20 second window of operation, this is not enough for a heat related issue, so I am more inclined to suspect the integrity of the Power Supply and/or the Motherboard (Where the infamous 'PON' originates) - In a basic configuration, the PON should stay on, even with other internal errors.

Now, that being said, No-Bus's suggestion of the 'BAD CAPS' should not be ignored as this was a MAJOR problem across the industry about the time that you PC was made and well worth the check, both in PCs, Power Supplies and Monitors.

rwalker1Author Commented:
I took the CPU off cleaned it and reapplied thermal paste which took care of the problem.
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