Motherboard battery replacement for Compaq Notebook

I've had my Compaq Presario 1830 for 4 years now and
recently I keep getting a black screen urging me to go
into setup and set my date, time etc before I can enter
windows. I am assuming that my motherboard battery is
dying or dead. Since this is a laptop, could anyone
confirm if [1] It could indeed be a motherboard battery
problem [2] if so, how can I go about changing it
(laptops are tricky and I'm no hardware guru)