I have had a red 'X' over the battery icon for while now, and its annoying when nothing is wrong with my battery (as far as I know).
It has constantly said "There is a problem with your battery, so your computer might shut down suddenly." and "Consider replacing your battery.".
I have a laptop that that charges in the wall instead of battery replacement. From the messages, my computer hasn't "shut down suddenly". Although when its off the charger is uses more power than it normally would before the issue.
Also, I don't think there is a place where a battery can be replaced.
Any help?