System boot & shutdown within 30secs

[weater]

I am having problems with my new PC. I built the computer myself and the parts are new. The specs are listed below:

PC Build specs
Mother Board - Gigabyte GA-965P-S3
CPUs - Intel E6300 Core Duo
Memory - 1GB (1 stick) Samsung
Tower Case - Shaw Super Sonata with 550W 4+20 PIN ATX & SATA
Graphics - GigaByte 256MB 7600GS
DVD - Pioneer 111D

1st system boot - POST process completed then shut down automatically within 20 secs while pending on OS boot disk (prompt).
Immediate subsequent boots - System didnot start up at all.

I waited for about 5 minutes and attempted to boot again. the above sequence repeated.

Could the above symptoms caused by the Mother Board short circuiting, CMOS prob, MB reset required, power connection, incorrect PIN connectors somewhere ...?

Since the computer has not booted up long enough, I have not been able to install the operating system.

Help !!!! Any helkp would be very much appreciated.

[Ob1]

i would double check all power connectors, make sure everything is securely fastened to the mobo and all components, did the processor come with a square of thermal paste already on the heatsink, if not did you apply the right amount if any? i was thinking that maybe the processor is overheating due to lack of thermal paste. review what connections go where on your motherboard and make sure they are seated correctly, lastly this one may sound stupid, but make sure that the DC power cable is securely fastened in the back of the PSU, i have seen loose cables cause issues just like this

[glc]

Those Socket 775 heatsinks are difficult to install properly. The 4 pins have to securely snap down into the holes before twisting and locking them. It's probably overheating and shutting down to protect itself. The heatsink must be installed when the motherboard is OUT of the case because you have to support the back of the board.

[Ob1]

i agree glc, those 4 push pins on the 775 heatsinks are pain in the rear, and if you have trouble securely fastening them to the mobo, then u run the risk of ripping the thermal pad causing it to not transfer the heat from the processor to the heatsink properly which can also cause your cpu to overheat or run hotter then it normally should which could shorten its lifespan.