Since a couple of days or so my laptop (asus n76vm) does a hard shut-down when the battery indicates 20% life left. It just cuts off the power, no shut-down screen or anything, making the hard drive do that nasty 'scratchy' sound.
What should I do now? It seems the battery is less powerfull than it was before (which makes sense) but the OS didn't keep track. How should I go about re-calibrating the battery?