|It's probably not booting up. You heard fans and drives spin up and some LED's flashed but that just means the hardware is getting 5 and 12 volts |
Was the PC working OK the last time you used it? Did anyone mess with it or did anything happen to it?
What about the video? If you originally had an on-board port and added a card, try both ports.
But likely the problem is with the power supply, motherboard or both.
You're not really green until you're soylent green.