Computer swiches off after 2seconds !

  Eargasm 23:11 19 Mar 2010

Trying to sort a friends computer running XP Pro When switching on psu and cpu fan spin all lights on case and keyboard work then it switches off after 2 seconds ( no beeps from the board even with memory removed)
I first suspected the PSU so replaced with a known working one but it was just the same.
I removed the memory and reset the CMOS , I then removed the processor and refitted the heatsink and fan applying new thermal paste, the computer then booted up, i ran various scans AV and Malwarebytes and nothing found. I updated the BIOS and installed latest Nvidia drivers the system ran fine each evening for nearly a week.
Last night the computer started but instead of the Desktop it was just a maze of coloured stripes on the monitor, my only option was to switch off the computer, since then it is back to square one, the PC will not boot switching off after 2 seconds.
I now suspect the motherboard ( but can't be sure) just wondered if anyone had any thoughts on what it might be ?
Just to add its onboard graphics, and if i hold in the reset button and then switch on, the computer then stays on, but no case lights or hard drive / DVD drive activity.
Totally baffled now any thoughts greatly appreciated

  woodchip 23:20 19 Mar 2010

Most likely is CPU is overheating. Check the CPU fan is working and Heat exchanger clear of muck

  Eargasm 23:45 19 Mar 2010

Hi Woody, Yes the CPU fan is working and i have had the heatsink out twice and it is as clean as a whistle, it seems like the system is shutting down to ( hopefully) protect the CPU. Thanks

  rdave13 00:04 20 Mar 2010

The maze of coloured stripes makes me think of the graphics chip now dead. Try a gpu card, check the slots for agp, etc, and if you have an old, compatible, graphics card that you can use, then try it out.

  Storic12 09:03 20 Mar 2010

Another thought. Did you replace the memory chips? I have found that faulty memory cause all sorts of weird problems. I'd bet on graphics card or memory - otherwise, sadly, motherboard, but hope not. New heatsink and fan?
Good luck

  woodchip 10:17 20 Mar 2010

sounds like a dry joint on the motherboard check round main power socket from PSU using a eyeglass. also check all plugs are full in. You could try a Basic boot with just graphics one stick memory no drives or pci cards or any USB

  woodchip 10:18 20 Mar 2010

PS if it as front USB remove the plug from the motherboard as these can be problamatic

  Eargasm 12:56 20 Mar 2010

Thanks for the replies folks, i have tried switching on with no memory installed and no drives connected but no joy.

rdave i did think the initial probles was with the onboard graphics, but it will not even stay on with no monitor connected.
I'm off to get another motherboard this afternoon i have found one a shade over £32, i will let you know how i get on.

  woodchip 17:09 20 Mar 2010

it as to have at lest one stick of ram to start

  Eargasm 17:16 20 Mar 2010

Woody, I'm not expecting the computer to start say to the desktop with no memory installed, but surely the power unit and cpu fan would stay on and beep if all was well ?

  retep888 19:24 20 Mar 2010

What make is the faulty motherboard?

Recently I had a similar problem with an Asus board, it was working perfectly ok then suddenly it booted up and died in 2 sec every time.

No beep, Psu fired up and died down , changed psu , tested every hardware, cleared Cmos, stripped down to barebone with nothing on, still the same, died down in 2 sec.

Finally, because it's a snap-on type of Bios chip, I just prised it out with a small screw driver and left it for a few minutes and refit, it's fine ever since (corrupted Bios?) weird!!

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