BIOS Battery

I have an old laptop thats not been used for some time, at least 3 years, and after some Googling and research it seems the BIOS battery may be dead. Where do I find the BIOS battery? Is it on the motherboard or a separate item? How can I test it? I guess it is a normal battery and it can be changed...yes/no?

Any help appreciated

In my experience the bios battery is on the motherboard,it's chrome,round and flat,like a large hearing aid battery,or calculator battery.

One clue is if the PC has not retained, or is unable to retain (when reset), the current date and time. Local computer shops sell replacement batteries.

Thanks guys, no it would not retain the date and time, have found a website that explained all, now I have to take the laptop apart to get at the battery.