The Molex connector, often known as the 4-pin peripheral power connector, is a legacy power connector widely used in older desktop PCs. It supplies +12V and +5V through yellow and red wires, with two black ground wires. Commonly found on 3.5-inch IDE hard drives, optical drives, and some cooling fans, the Molex connector provided a reliable power solution before SATA power connectors became standard. Its robust design ensured secure connections, though it is now mostly used in retro systems and adapters.