Some key computer functions are governed by the CMOS (Complementary Metal-Oxide-Semiconductor), a chip on your motherboard powered by a small battery.

This CMOS battery lets the system clock keep running even when the computer doesn't have power, and allows the motherboard to store small amounts of data in active memory.

The CMOS battery is an often overlooked but crucial element. Hidden on the motherboard of your computer, it acts like an emergency power supply for the BIOS.

If something has gone catastrophically wrong with your PC, you may need to reset the CMOS to solve the problem. Here's what you need to know.