Help please...PC shuts down unexpectedly.

[Alexfan]

I hope someone can help me diagnose the problem I am having with my PC. These symptoms are fairly repeatable:

1. PC boots up fine, but shuts down unexpectedly within 1 minute (like the switch at the back of the computer was switched off).
2. Computer is dead for ~3 minutes (although red LED on motherboard is on).
3. First sign of life is the green LEDs on the keyboard which start flashing quickly and then settle down.
4. About a minute later pushing the power button on the front of the box gets it going again.
5. Steps 1-4 repeat again, except time before shutdown is now 2-3 minutes.
6. Computer starts up OK and usually stays on at the third attempt.
7. However, switching our DSL modem off or plugging an MP3 player into a USB port will cause the PC to shutdown...and back to step 2.

It's hard to pinpoint exactly, but the unexpected shutdown seemed to start after I installed an old HP burner on my PC, although when I removed the burner the problem persisted. The PC was dead for ~3 minutes and then came to life. It's like something is shutting power off to the motherboard, maybe a short or a safety interlock or something.

Here are my details:

P4 2.6 GHz Albatron 865PE
512 MB DDR400 RAM
Windows XP Pro SP2
North Antivirus 2005 (with latest updates)
HP 9100 burner
LG DVD Player
3.5" floppy
Fujitsu 9.5 GB hardrive with 3 GB spare
ATI Radeon 9200 Video Card

If anyone has any suggestions on what could be causing this unexpected shutdown, I would be very grateful.

Thx.

[kiosk]

Check the mainboard for bulging/leaking/gunky capacitors. While you're in there, replace the CR2032 lithium button cell battery.

Your power supply could be failing as well, especially if it's over two years old - they contain capacitors as well, which are just as likely to go bad as the ones on the mainboard.

[Whyzman]

What size and make of power supply are you using?

[Alexfan]

Thanks for your help kiosk and Whyzman.

My system was built in May 2005. It is a clone. The HD, CD and floppy came from an old system. The HD was wiped clean.

My power supply is an Orion XP400, 115/60/6A Max 350W
Output +12VDC 15A Max

[Sylvander]

Load and run Knoppix from a Knoppix Linux Live CD (http://www.knoppix.net/get.php).
If it runs just fine, with no sign of the previous problem, then there's nothing wrong with your hardware [HDD excluded] or the BIOS or its configuration settings.

You'd know it was a software problem; the Windows environment [or the HDD].
Are the BIOS's configuration settings for the HDD OK?

The converse is the case if the problem is still there.

[Vallan]

It's possible that when you installed the HP burner, you accidentally knocked the processor fan cable loose. Or the fan itself may be failing. It may be shutting down to prevent the CPU from overheating. Checke to see if it's spinning and has a solid connection to the board.

[Alexfan]

Thanks for your replies Sylvander and Vallan. I checked the fan cable, and the fan itself, and it seems to be OK.

Through some additional detective work I'm 90% sure I've isolated the problem to my internet connection. With the internet connection (i.e. ethernet cable) unplugged, my PC starts up and runs fine. No problem plugging an MP3 player or memory stick into a USB connector either (which previously caused the computer to crash, but the internet was always on). So it looks like the internet connection is causing the shutdown problem.

My PC connects to the web via an ethernet cable and a Siemens SpeedSteam Model 4200 Modem. The Ethernet cable goes straight into the LAN connector on the motherboard, so no driver is required for the Modem. Switching the modem on and off invariably caused the PC to shut down. However, sometimes it would start up and stay on for hours as long as the modem was not turned off.

I hope this new information is helpful....thanks again for any suggestions that can help me resolve this problem.

(Right now I'm connecting with an old PII 333 PC via the Siemens Modem but using a USB port connection rather than the ethernet/LAN connection because my old PC does not have a LAN connection. So far no problems with the modem or the PC...just the speed!).

[Sylvander]

1. My guess...

a. Some kind of software problem. [Does it exist in Knoppix, and/or Safe Mode with all hardware connected?]

b. Probably a software conflict.

c. Most likely a resource conflict.

d. IRQ conflict top of my list of suspects.

2. Images 1 & 2 below show my PC's IRQ usage.
Image 2 shows IRQ's being shared without problems.
I know little about how resources can be shared without problems.

3. I suggest you go to your Device Manager, display in various modes [like "View>Devices by Connection"], and study the problem devices and their resource usage.
You could disable the modem [or USB] in Device Manager.
Finding which disabled device and eliminating its [conflicting] resource usage might point to the cause of the problem.

4. You may need to tweak "BIOS Setup>PnP/PCI Configuration" settings.
Like "Force Update the ESCD" [with all hardware connected] by...
Reset Configuration Data : Enabled
Then "Save and Exit Setup".
And...
Resources Controlled By : Auto
PnP OS Installed : No

5. When you switch hardware on and off...
Windows must smoothly readjust to the new hardware arrangement using registry settings and driver files.
Obviously that isn't happening.
Perhaps an XP Repair Install (http://www.michaelstevenstech.com/XPrepairinstall.htm) is needed to fix that.
See also XP's No-Reformat, Nondestructive Total-Rebuild Option (http://www.informationweek.com/windows/showArticle.jhtml?articleID=189400897).

Images 1 and 2...