Final answer:
The CMOS battery or CMOS RAM is the BIOS component that stores configurable settings and keeps the system clock running when the computer is off.
Step-by-step explanation:
The part of the Basic Input/Output Services (BIOS) that stores the changeable aspects and keeps the computer clock running when powered down is known as the CMOS (Complementary Metal-Oxide Semiconductor) battery or CMOS RAM. The CMOS battery provides power to a small amount of memory that stores the BIOS settings. These settings, such as the system time and hardware configuration, remain persistent even when the computer is turned off because the battery provides a constant power source to retain the information.