Moet likely you have the power button connectors mixed up and on the wrong pins, the computer should not start up when you plug in the psu. Does your psy have a switch on it to turn the psu on and off? You can use that instead of unpluging untill you get the power button straightened out. If you changed the cpu you have to make sure that it supports the onboard video. Have you gone into the bios and made sure that the onboard video is enabled?