My battery started playing up a few days ago and now it is showing the [X] symbol for "Battery not available". I almost always work off mains power using the power adaptor so the battery has not been drained of power for ages. I think maybe this is the problem and the battery needs replacing. However, there are some odd things about it that make me wonder if the battery is really dead. First, I tried booting from the mains adaptor and pulling the power lead out of the macbook as it booted and it actually continued to boot for a while. I think it got as far as the desktop screen, then it shut down. So, there must presumably be some power in it? In addition, I pressed alt and clicked the batttery [X] icon and it showed this (screenshot below). How can my battery's condition be "Normal" and yet the battery is not recognised? I don't want to pay for a new battery only to discover that the battery is fine and there is some other problem. Any assistance would be much appreciated.