Computer random shutdowns

Have a PC here that will just switch itself off at random, by switch itself off its like someone pulling the power chord - no BSOD, no warnings, nothing. It is totally random and can go days or a week without doing it or may happen three times in the same day.

I've run memtest on it with no errors, CPU temp is around 46 at idle and up to 60 at full load, PSU is a heavier duty one (680w), hard disk has been scanned for nasties using several software solutions (Malwarebytes, Spybot, A-squared, Avast). Have done all the usual checks.

It also is very slow at startup and boot, I've turned off everything non-essential and streamlined the process but to no avail.

Specs as follows:

Win XP64 Pro SP2
AMD X2 5600+
4GB DDR2 Kingston 6400
ASUS M3A78 board
Nvidia 9800 GT 512 Graphics
Seagate SATA 300GB HDD

Any suggestions on what else to check or any full diagnostics software recommendations?

"Have done all the usual checks."

Hard drive diagnostics?

Anything in Event Viewer?

If you are confident that your line voltage is stable (circuit not overloaded, no brownouts, etc.) than you are pretty much left with a failing voltage regulator on the mainboard or a defective power supply. PSU would be the leading candidate, assuming no obvious problems with leaking capacitors on the motherboard.

Motherboard is where i would look

Thanks for the replies, I've tested the hard disks with Seatools and they come up clean. The Event Viewer shows this around the time of the shutdowns:

Code:

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\SystemRoot\SysWow64\drivers\pfc.sys has been blocked from loading due to incompatibility with this system. Please contact your software vendor for a compatible version of the driver.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.

---

A quick search tells me its something to do with optical drives, doubt it would shut the machine off entirely.

Regarding the stable voltage, this is unlikely as I am based in Thailand (where things are generally unstable). However the other computers in the same office do not suffer this problem. I have had a UPS before but they fry quite often here so didn't replace it. Do you think getting one will solve it?

Regarding the mainboard can you recommend any diagnostics software to test it?

There isnt really any testing software other then a burnin test which may or may not depending on the software create a log and detail why it crashed. Usually the motherboard is inspected visually carefully to see the caps if they are swollen or weeping.

As to the pfc issue, you can try removing the upper and lower filters for the CD Rom per; http://support.microsoft.com/kb/314060

I got this idea from here; http://www.planetamd64.com/lofiversi...php?t7224.html

re the unexpected shutdowns; have you confirmed the mobo main power plugs are making good contact. While inside, verify that the cpu heatsink is well and truly attached and the fan and heatsink are clean. Also, shut down and pull and replace the power cable a couple times to wipe the contacts.

As a last thing, if you are in an office, they should spring for a backup psu and that would be a good thing to then install.

I have had a UPS before but they fry quite often here so didn't replace it. Do you think getting one will solve it?


Yikes! If a U.P.S. fries often, you have serious power issues. Most battery back ups are proof against power fluctuations, and if they are going then you need power filters IMHO.

Yeah power supply and internet connectivity is somewhat archaic where I live!

Will follow the advice given and look into getting a decent UPS.

Cheers.