Connecting all the various pieces and parts of your computer may get confusing especially if you do not know which cables go with which connector. Manufacturers use color-codes to make the connection even easier. If you're not sure what color cable goes with what device, you can view this quick reference explaining the different types of connectors in the back of your computer. System Connector Reference
CAUTION: Make sure that every cable is firmly connected both to the system unit and the specific piece of hardware. Loose cables can cause all sorts of problems.