The motherboard is the heart of a PC. Some manufacturers use the terms system board, planar board, baseboard, or main board, and Intel calls their motherboards desktop boards. No matter what you call it, the motherboard defines the PC. It provides the common link to all other components inside the PC, including the CPU, memory, disk drives, video and sound adapters, keyboard, mouse, and other peripheral components. If you are building a PC, choosing the motherboard is the most important decision you make and can be one of the most difficult. If you are upgrading a PC, replacing the motherboard is often the best and most cost-efficient means of doing so. If you are buying a PC, the motherboard it uses determines its functionality and future upgradability. This chapter describes the characteristics of motherboards, provides purchasing guidelines, and explains how to install and configure a motherboard.