My 2007-era MacBook Pro 15in is shutting down abruptly after only running for a few minutes after booting. I've already changed the battery, and it actually stayed running for a few days after that, sitting undisturbed. But on the third day, it went back to abruptly powering down, and if I try to immediately boot it up (using the start button), it doesn't even finish starting up before abruptly turning off. But if I let it sit for a few hours afterwards, it starts up, stays running for a few minutes (at most about 3), then does the abrupt shutdown. Not a mormal shutdown. One that looks like the battery is out of juice with no power adaptor connected. But the battery is fully charged, and the power adapter is also new and connected.
Any advise (other than cannibalizing the hard drive to make an external drive)?
Thanks in advance.