Power error in POST

[Guest]

Just built my first PC and having some issues getting it started up. Had everything plugged in and connected and was getting the power error beeps.
I've now unplugged everything from the motherboard except CPU & heatsink, and the cable from the case to switch on the power. Still getting the 'power error' beeps.

What would you all recommend I do next?

 

[Guest]

Just adding some details -
PSU - 500W silverstone.
CPU - Core i5 760
MB - Gigabyte 355a-ud3
RAM - 2x2gb sticks of ram EVM brand.
Video card - Radeon 5770
HDD - 1gb Seagate

 

[fellskrazykayaker]

Did you make sure all auxiliary power connectors are plugged into the motherboard?