When I turn the power supply on and press Switch it starts but before windows start it turns off.?

When I turn the power supply on and press the switch of computer it stats but before windows starts the computer turn off suddenly and after that when I press switch of computer nothing happen. I have changed my main board with anew one and also I have changed my power supply with another one, but the problem... show more When I turn the power supply on and press the switch of computer it stats but before windows starts the computer turn off suddenly and after that when I press switch of computer nothing happen. I have changed my main board with anew one and also I have changed my power supply with another one, but the problem persist. My computer has the following specifications:
Intel P4 2.4 512 Mb cash
1024 Mb DDR RAM
128 Mb graphic cards
I want to know can I use a power supply 370W or less for my computer? Or it should be 400W and up.
I hope somebody can help me for this problem
Regards
Ali
Update: Where is this Setup that you have written?
7 answers 7