laptop battery

So ive gotten this Panasonic CF-R1 mini notebook from a friend; slightly used, no real wear and tear. everything is fine with it, but the battery is a bit off. i fully charge it, and it discharges fine till it hits about 46%, and then it drops immediatly to 9%, then slowly to 5% and stays there for an indefinite amount of time. so my guess is that there is some kind of battery memory problem- it thinks its almost empty, but its not; it can sit on %5 for a good hour or so, never changing. i've read about a similar problem with macs that can be fixed with a few lines in the firmware menu. does anybody know if there is a windows 2000 equivalency? or is there some other way to fix my little compy?
thanks.

oh shit, i just realized "COMPUTERS HAVE THEIR OWN FORUM. This forum is not for computer discussion." well, fuck. maybe since its about the battery, hopefully ill be allowed.

Please repost in the computers forum, thank you.