I can't find computer problem!

I currently have a computer which has quite a bit of a problem that I cannot locate. Whenever you try to boot up the computer, it passes the BIOS, and power on test but once it starts to boot into Windows 7 the computer automatically switches off.

I have tried to locate the problem, and have tried the following things to fix the problem;

Reseated all cables, still wouldn't boot
Removed the hard drive and put it into another computer, and it successfully loaded into Windows.
Ran a RAM test, no errors
Ran a hard drive test, no errors
Used a different graphics card, still wouldn't boot
Used a different power supply, still wouldn't boot
Used a different CPU, still wouldn't boot
Took a hard drive out of another computer and put it into the one that wouldn't boot & it still wouldn't
Replace the RAM, still wouldn't boot
Removed all PCI card, still wouldn't boot
Disconnected optical drive, still wouldn't boot
Disconnected all peripherals, still wouldn't boot

I have replaced or disconnected almost every component within the computer, apart from the motherboard and once it got to the Windows load screen it still shut off. The only component I have not changed is the motherboard, so it must be at fault?

Thanks for all help!

 

not sure if you still have a problem with this, but what are the specs of the computer?

 

Better you give your computer for a service .That would be a better option.

 

Have you installed new RAMs recently?

 

Does it do a blue screen just before it powers off?

 

this could literally be anything!

 

use tune up utilities,
it will find any problem automatic,
and fix auto too

 

Might also be a power supply issue.

 

I'll betting on your motherboard.