Power supply -- Other than its CMOS, which is powered by a replaceable CMOS battery on the motherboard, every component in your PC relies on its power supply. Central processing unit (CPU) -- The CPU, often just called the processor, is the component that contains the microprocessor. That microprocessor is the heart of all the PC's operations, and the performance of both hardware and software rely on the processor's performance. Random-access memory (RAM) -- Even the fastest processor needs a buffer to store information while it's being processed. Drives -- A drive is a device