Operation shutdown randomly

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My 10-month old pc (pentium4 ht, xp home sp1 sp2) stopped operating randomly
1 to 15 minutes after turning on (the power light still on, fan still
running, power supply unit still getting warmer, but the screen is either
black/blank or displays a small window that appears when the monitor is
turned on without the pc on). Possibly similar problems have been posted
herein (e.g., silent kelly 6/8/2005) and replied helpfully. It was pointed
out (segovia 6/9/2005) that the cause could be one of many things in both
software (e.g., spyware or malware infection) and hardware (bios,
overheating, fluctuating voltage, memory, etc.). I tried system restore,
repair install but the pc did not remain operating long enough to allow
completing the task. Now, it does not even boot. A diagnostic software told
me there are "critical errors" in the file structure. I could try a
clean-reinstall xp but suspect it will be stopped midway as before. I
cleaned out the fan, ventilation window and even left open the enclosure
panel, but the problem persisted. The inside became only slightly warm
anyway. I did notice, however, the pc stayed operating the longest (15 min)
the first time it was turned on after a night off. The operating time
decreased when I kept turning the power off then back on again and the pc got
warmer. There were times the shutdown occurred even before windows was fully
loaded. Would appreciate any comment/suggestion/advice or further question.
 
What diagnostic software did you use?

Well here's the deal:
Even if there are critical errors in the file structure you should be able
boot into your XP boot disk and do a reapair from there. Since you can't even
do this then the biggest problem lies with your hardware.

Here are some possibilities:
1) CPU is overheating - check if the CPU fan is spinning at different points
after you try to boot your computer.
2) You could have a bad Power Supply - places like Comp USA can check this
for you.
3) Bad RAM - you can download and run Memtest86.
4) Faulty graphics chip/card - places like Comp USA MIGHT be able to check
this (but I wouldn't get my hopes up)

If number 1 is the case then you might not notice much of a temperature
increase inside your case.

If your computer is still under warranty (probably at least up to a year)
then you should contact the manufacturer and see about shipping it back to
them so that they can repair it for you.

If you don't want to send it back then you can get a program called Speedfan
- http://www.almico.com/speedfan.php - and check the 'core' temperature -
this will tell you if your CPU is overheating. For the power supply you could
swap it for one in a different computer (if they both have the same case type
- i.e. ATX etc.). For bad RAM run Memtest86 - if you get a lot of errors
replace the RAM. For the graphics chip/card it's a little more tricky - if
you have a graphics card from another computer put it in the one with the
problem see if it still messes up.

Past this the only other thing I can think of is that maybe a power surge
fried your motherboard. If you have a surge protector then this might not be
the case - unless you have dial up internet - I've seen a computer get fried
from a lightning strike surge going through the phone line. You could try
swapping your motherboard with one from another system.

-Dan
 
PowerQuest was the software. I also used it to perform a memory check which
passed. The other possibilities you listed I cannot rule out. I'm inclined to
return the pc to the manufacturer along with a copy of your message. I much
appreciate your very detailed reply.
 
Doors stop working throughout the house. Therefore you get new
doors? No. Start by verifying fundamentals such as the foundation and
floor beams.

Same applies to a computer. Its foundation is the power supply
system. Not just a power supply, but a system.

Solution starts with verification - eliminate what could be reasons
for failure. Two minutes with a 3.5 digit multimeter can identify a
power supply system as good or defective. Once a power supply system
is confirmed, only then are you ready to look at things 'supported' by
that foundation; ready to perform diagnostics.

In your case, system can be confirmed by measuring voltages on a
purple, red, yellow, and orange wire from power supply to motherboard
(voltage between each wire and black (ground) wire). Voltages should
be above 4.87, 3.23, and 11.7 VDC. Furthermore, those measured numbers
may identify other useful facts.

Voltages should be sufficient when systems starts AND remain in spec
when peripherals are accessed - by Windows or by diagnostic. Without
first confirming the power supply system, then numerous and strange
failures may appear and confuse. Only after a 'foundation' is
confirmed - especially when power supply is under load - are you ready
to move on to diagnostics - to look for other reasons for failure.

Meanwhile, heat is a diagnostic tool. A failing component will fail
more consistently when hot. A good component will never fail even when
a sealed up computer operates in a 100 degree F room. Heat finds an
intermittent problem - how to make the intermittent obvious. Another
tool to finding a defective part is a hairdryer outputting heat on
high.
 
Do I understand you correctly, Tom, that the voltage should be at or above
4.87VDC at the purple wire, 3.23 at red, and 11.7 at yellow? If so, what
about orange?
 
Simply measure each voltage. It will be obvious which are 3.3, 5, and
12 volt wires. No reason to memorize anything but the four colors.

Meanwhile, purple is 5 volts (> 4.87 volts) when computer is powered
on or off (which is why power cord must be removed from wall before
doing anything inside the computer). Other colors are only powered
when power switch is pressed. Red: 5v. Orange: 3.3v. Yellow: 12v.

Other significant wires (but not related to your problem) are gray
and green.

Pictures on using a multimeter:
http://techrepublic.com.com/5102-10586-5566528.html

But which color wire is which voltage? Either the wire will be at or
slightly below its voltage, or wire will have no voltage. Voltage on
each color, when posted, may provide others with additional facts.

Two minutes to confirm power supply integrity - and then move on. Do
not remove power supply since best test is supply under load; best
testing load is the computer.
 
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