[ Desktops ] Open Question : Building a computer. Need help?

I'm in the process as I am typing this putting together a computer (I have all the parts as I'm just putting it back together) The motherboard is getting power (The green indicator light is showing) But when I click the power button I don't get a boot up. The neon lights and fans don't come on either, but the green light is on. I'm curious if hooking up the HDD, HDD_LED (All the little green/white, red/white 1-2 pin cables) has anything to do with the power, or if there is something else that I'm doing wrong. I have a Asus P5N-D motherboard if that helps anyone at all.