My computer won't power up

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1

This is my rig.  I put it together recently but it won't power on.  What should I do?

CPU- Intel Core i5

Motherboard- Asrock H61M-DGS

RAM- G.SKILL 4GB (2 sticks of 2GB) DDR3

GPU- Sapphire Radeon HD 7850 2GB GDDR5

Hard Drive- Samsung 250GB

Optical Drive- DVD Player

Power Supply- ThermalTake 500W

Case- ThermalTake Commander Case Snow Edition

2

clear the cmos, check the psu is on, check the wall plug is on.