Final Connections

If your connections are different.
Check your motherboard manual. All good motherboards come with a detailed manual, which has diagrams for your particular board. By referring to these diagrams, it is very easy to see which connectors go where.

If you are using an AT style motherboard.
If you are using this type of motherboard, the power connector that goes from the power supply to the motherboard itself will be in 2 sections. They will be labeled P8 and P9. These must be connected properly if you wish to see the motherboard ever work. THE BLACK WIRES MUST BE PLACED TOGETHER WHEN PLUGGING THEM INTO THE MOTHERBOARD!!!

Final Connections Checklist
Drives properly connected to power?

CPU fan attached to power?

Power switch is off?

The 110/220 volt switch is configured properly for your area?

Ribbon cables attached correctly, red edge on pin 1?

Are all connections tight, no connectors off by one set of pins?

Cards fully in slots?

No wires protruding into fans?