I have used two different power plugs and it still won't power on, I did notice that there is no memory sticks on the board. In the past pc's would boot w/o memory being installed but would error on post. Do the HP's have to have memory for them to power up? If not what could some other causes be? The power supply itself shows a green light on above it when plugged in as well but when I press the power button I get nothing.