My iBook has lain dormant for the last 6 months. The battery of course has therefore run down. I plugged it in to power, left it plugged in overnight. But when I turn on the power switch, I heard a whirring noise, and then silence. a couple of times, it actually powered up and my desktop showed up, but then in a few seconds, it turned itself off. Is there any way I can get the computer to tun on and stay on?