i bought my macbook pro last july, and since july, i calibrated my battery once a month, and since i had a powerbook before, i calibrated my macbook pro battery now just like how i calibrated my powerbook battery before... so last night, i drained my battery to zero, so it would eventually go to sleep as usual, and the warning came, saying that "you are running on low battery" as usual but instead of sleeping it shuts down.. i have to turn the power button on again, and plug it in the power. so my question is, is something wrong with my mbp? is it suppose to sleep when the battery reaches zero? but why did my mbp shuts down last night instead of sleeping? it only happens last night only, but before that, it always go to sleep... and my second question, i've been doing the powerbook method of calibrating the battery, but last night, i just saw in the apple website that, the macbook pros have new method of calibrating its battery which is,...... PowerBook G4 (15-inch Double-Layer SD), MacBook (all models), MacBook Pro (all models), and MacBook Pro (17-inch) (all models) The battery calibration for the PowerBook G4 (15-inch Double-Layer SD) and any model of MacBook or MacBook Pro has been updated because of a new battery released with this computer. With these computers, follow these steps to calibrate your battery: Plug in the power adapter and fully charge your PowerBook's battery until the light ring or LED on the power adapter plug changes to green and the onscreen meter in the menu bar indicates that the battery is fully charged. Allow the battery to rest in the fully charged state for at least two hours. You may use your computer during this time as long as the adapter is plugged in. Disconnect the power adapter with the computer still on and start running the computer off battery power. You may use your computer during this time. When your battery gets low, you will see the low battery warning dialog on the screen. Continue to keep your computer on until it goes to sleep. Save all your work and close all applications when the battery gets very low, before the computer goes to sleep. Turn off the computer or allow it to sleep for five hours or more. Connect the power adapter and leave it connected until the battery is fully charged again. so i've been doing the powerbook method of calibrating my battery since july, which is i plug the power as soon as my macbook pro goes to sleep,... is there something wrong? would it harm my macbook pro? and now the health of my battery is 99%.