Have this MacBook Pro from 2009, 2.53GHZ, A1286. It will boot, show the Apple logo, and sometimes get to the desktop. Very quickly after it will turn off completely, as if someone pulled the battery (computer completely turns off, not just the backlight or screen). So far my troubleshooting has been: -Tried swapping both RAMs into each slot respectively. -Tried booting from a USB flash drive with HD removed. -Tried booting the computer from a charger with the battery unplugged. -I tried the NVRAM zap and SMC reset. The only thing that fixed it temporarily was leaving the computer unplugged completely with the battery unplugged overnight. Then it worked fine, until the battery ran itself down and I tried booting it this morning with a charger plugged in. Any ideas?