Crappy Lenovo Battery

[ChrisM]

Hey guys, I've just noticed on my old laptop, that in the System Icon area of the taskbar, my battery icon says "Consider replacing your battery".

When I click on the battery icon, it says " There is a problem with your battery, so your computer might shut down suddenly," - this is when running off the charger, and "100% charged"

Now, its not an ancient laptop, and I'm a sucker for always having it charged and not very often does it actually run on the battery alone, so my question is, whats the reason behind the message? Has it been charged too many times, or is charging it constantly bad for it? Any suggestions? More specs can be posted if required.