take your entire build out of the case. If you have dvi-cable, that might be helpful.
Start by reconnecting everything, make sure your gpu is sitting firmly in slot x16 nearest to cpu. Connect your keyboard to motherboard and monitor to your gpu. Check the pcie connectors, hoping you are connecting 2 of the 6-pin connectors in the gpu power source. Re-seat your ram, check with single ram. Make sure you really don't have any bent pins of your processor. Connect the power supply to motherboard and cpu connector. Power up the psu. Does it show anything? Press NumLock key on your keyboard, is the light on keyboard for NumLock turning on and off?
Next step is to clear your CMOS and recheck.