Hi. I'm not new to OS X, but I am new to MacBooks. I've recently been using the MacBook in the title: Model Name: MacBook Model Identifier: MacBook3,1 Processor Name: Intel Core 2 Duo Processor Speed: 2 GHz Number Of Processors: 1 Total Number Of Cores: 2 L2 Cache: 4 MB Memory: 1 GB Bus Speed: 800 MHz OS: Snow Leopard, 10.6.8 It's been lightly used over the years, and never had a problem. Yesterday, the Mac immediately shut down after I removed the AC adapter. Each time I tested this, I got the same result. I ran Disk Utility, and everything is reported as fine. The battery is recognized and reported as fully charged in both the menu bar and System Profiler. I've rarely used the MB with battery power, and the battery is in good shape. I was working on it about a week ago for about two hours with the battery alone. It had plenty of power left when I plugged in the AC. I don't have a spare battery to test. All help will be greatly appreciated.