EVGA NVIDIA nForce 780i SLI and PSU won't start

I've built two other pc's before and they've turned out just fine. Though I am finally having a problem with building my OWN first pc. Everything was set up perfectly, but when I hit the power switch/button, nothing turned on. so I opened the case and watched it. hit the power switch, a yellow light appeared, nothing turned on. so When i turned off the switch. the green little light turned off and it turns on once I hit the back switch.

So i have it outside of the case trying to POST it. the psu connected to the mobo --- main connector with it's little 4 pin addon next to it. the two 4 pin cpu wires going onto the mobo as well. psu also connected to the graphics card. has 1 stick of RAM in the dimm0, cpu with it's headsink on it with the wire going to the cpu fan.

same result. plugged in, switched turned, green light comes on, hit the power button, yellow light comes on, nothing else does, but that. HELP PLEASE

Welcome to Nvidia chipsets.

Do you have another power supply you can use to rule out the PSU? Or another working mobo to rule out the motherboard?