Please list all your specs including the video card and the brand name and wattage of the power supply. Then, tell us exactly what happens when you push the power button.
In addition to what tumbleweed36 has said, double check that all your power connections are in fact on and connected. Also before doing anything else I would suggest trying a different power lead, before going down any other route.
A forum community dedicated to tech experts and enthusiasts. Come join the discussion about articles, computer security, Mac, Microsoft, Linux, hardware, networking, gaming, reviews, accessories, and more!