There is a flashing green light when i press the power button

Just in case something got wiggled, try unplugging the power supply again, press in the power button and hold it in for a count of 10 seconds to dissipate any internal power, then open up the chassis again. Make sure that all the power connections that run from the power supply are seated tightly into the connectors on the board. Take the memory out again and make sure that you re-seat it tightly.and for more info http://tinyurl.com/m7ghqz