Computer shuts down during startup

[CapnTom]

Help please !
My computer, which has worked OK for several months has developed the following fault :
During startup the power is suddenly cut and the computer completely dies.
The problem is intermittent, sometimes it happens during the POST period, sometimes after the windows screen has come up, but before the Windows startup has completed. If I get as far as the Windows log on then everything is OK and there are never any problems until I next shut down.
If I enter the BIOS setup at startup the computer will still power off as I navigate through the options.
Shutdowns still appear if I boot to a bootable, non-windows floppy
Once it has failed, the computer won't restart until I have switched the mains power off and on again.
I have not made any hardware or software changes to the computer recently.
I have tried opening up the computer and practically dismantling it, disconnected all leads, peripherals, expansion boards and memory modules. The problem disappeared for several days after this action but has since returned.
I suspect a power supply fault or motherbaird failure.
Any advice would be appreciated before I spend cash on new components.
Regrds, CapnTom

 

[ravenmadtaoist]

I had similar problems when my power supply was dying on me. Haven't had them since I installed a new one.

 

[CapnTom]

Thanks for the posts,
My system :
P4 2GHz, 200FSB
Giga-Byte 81RXP motherboard
1G of DDR PC266 memory (Kingston)
NVidia GeForce 4 Ti 4600 graphics
Running Windows XP on 3 seperate hard drives (Maxtor 40G )
Individually bootable through a Romtec Trios hard drive selector.
PSU is 400W P4 certified

Thanks again for your efforts.
Regards CapnTom

 

[Lostman]

What brand is your power supply? I've had some cheap ones that have crapped out on me in the past.

Also, when you say shuts down, does it just die and go to a black screen or does it reboot?

It does sound like a power supply issue though.

 

[CapnTom]

Hi

My power supply is a TTGI model TT-350SS (350 watt)
The shut downs I have been getting have been exactly as if I pulled the mains plug for a second, complete death !
Also, after each failure the computer doesn't respond to the front panel on/off button until after the mains switch on the PSU has been switched off & on again.

Regards, CapnTom

 

[Lostman]

I would bet that it's your Power Supply. Your statement about the front panel button is what does it for me.

Go out and pick up a name brand power supply. It might cost you $50 or $60 for a cheaper one, but I think that might solve your issue.

 

[CapnTom]

Thanks to all who helped, I bought a new power supply and everything seems to be OK for now.

Best regards
CapnTom