Any thoughts on why my laptop won't power up?

It’s three years old and I used it last night and it shut down normally. This morning I hit the power button and nothing happens. The disk player opens and if I insert a disc it clicks a few times, but doesn’t play. Or if I hold the power button down for longer than five seconds and the hit again the lights flash, but it still doesn’t start. It’s got power, but it won’t start up with anything I’ve tried. Any thoughts?