The internal components of the desktop system unit are laid out horizontally (as opposed to the vertical |tower system|). Among these components are the motherboard, fan, internal speaker, expansion slots, disk drive (or drives, if any), power supply, and chassis lock. Additional cards such as expanded memory, video, or sound cards may be present.
Consideration must be given to the size and capacity of a desktop case when choosing a system. The older XT cases are smaller than the more recent AT styles, and so some motherboards and components will not fit. In fact, some users find even the AT case to be too small for an extended array of additional components. They may opt for the larger, free-standing tower case, which also frees their desktop of additional clutter.
