Computer hardware issue

[Hummer]

A look at the inside of the PC prior to cleaning. Not as bad as I've seen in other units. The fins behind the fan on the circuit board held the most dust and I suspect this was the source of the off and on fan surging.

Notice that there's a 2032 button battery on the circuit board. I wouldn't expect it to hold much juice after 6 1/2 years. What would this be for and should I replace it?

[FoxtArt]

A look at the inside of the PC prior to cleaning. Not as bad as I've seen in other units. The fins behind the fan on the circuit board held the most dust and I suspect this was the source of the off and on fan surging.

Notice that there's a 2032 button battery on the circuit board. I wouldn't expect it to hold much juice after 6 1/2 years. What would this be for and should I replace it?

CMOS battery. It powers the BIOS, which is the initial operating system that loads when you turn the computer on (e.g., not Windows, the power-on-self-test stuff). In short, if the battery dies, nothing happens except it doesn't remember what time it is and will give you a notice to that effect. I wouldn't worry about swapping it, it may outlast your desire to use that computer.