Green light on the motherboard is on but computer won't start when press power button. all components of system are working fine ram, hard disk, cpu fan, smp when i checked all components in other system .
Your going to have to be little more specific. So my question is this: So when you plug in the power cable into the psu and flip psu to the on position, you see the lights of the motherboard and everything but when you press the on button to turn on the computer, nothing happens? The power button doesn't light up and pc doesn't boot? Or do you mean you hear the system boot but nothing displays on screen?
Go through the normal testing then, disconnect all drives then try to post. If not then move to ram, psu, cpu, then motherboard test. Then after that breadboard to rule out shorting out. I would actually test the psu first now that I think about it.