I've had a brand new MacBook for about 6 weeks. All was well until today when I notice that the battery is showing 0%. The computer works with the adapter in but of course immediately goes dark if I unplug it. This is the first time this has happened. I did the "drain the battery and recharge" thing when I got the computer and as I work on both battery and power intermittently, it has gone low many times and then left to recharge. Help! Any ideas? I'm a neophyte here...