Alienware Area 51 not powering up

Had this computer for several years. Never Had a serious issue, until today

Before leaving the house, I put the computer to sleep. When I came home, I hit the power button, and it started coming back to life. Then it went dead. Looked at it like a deer in headlights for a min. Then hit the power button again. Same thing. So. I figure third times the charm. Hit the button....nothing.So. first thought it power supply. Not powering up, no lights one the outside on. So. I pop the side open, and the internal lights ARE on. So I don't know if it's ower supply (line going to thepower button or motherboard) maybe.bit of its the button it self. I/O board....have no idea how to test any single component.

Tried different power cord to computer. Unplugging and holding power button, different outlet with and without surge protector....I'm lost guys. ..