The A/C plug, that is... Today I made the plunge and purchased my first Macbook. After opening the box, I plugged in the large A/C plug and let it charge. Now the light is green after two hours, however, I just wanted to quickly ask... do I unplug the A/C cord before I turn it on or do I leave it plugged in? I had heard that the battery needs to be calibrated before using the Macbook... if so, does anyone know how that would be done? Excuse my ignorance to this... completely new with these things. Thanks!