pc wont turn on HELP

Ive got a ASUS P5GDC Deluxe with a P4 processor(both are brand new). Im running xp pro and I cant get the pc to turn on. If you look inside you can see a a green light indicating that its receiving power but when I hit the power button I get nothing. Is this a tower problem or a board problem? I have a ATX case w/ 350 watt power supply, also brand new.