shutdown after windows load

hello gys i have a problem in my computer when i turn it on and giving the windows load logo it shutdown automaticly and i cant turn it on until i unplug and plug the power supply wire.i tried every think i buyed the thermal past i changed rams barrs everythink i tryed safe mode and all the F8 list

Note:
the button of power start blinking

hope you solve my problem thx techrepublic