How to bring a dead MacBook Pro back to life
First, tether this MacBook Pro to a working Mac with a Firewire port. Attempt starting the MacBook Pro to Target Disk Mode. While the working Mac is on, and the MacBook Pro is off–but connected to power–and both computers are connected to each other via a Firewire cable: press the power button on the MacBook Pro and immediately press and hold the T key on its keyboard. Normally, you will begin to see a Target Disk Mode screensaver on the target Mac and its hard disk drive will mount to the filesystem of the working Mac. If neither the screensaver appears or the drive is mounted, check the System Information app on the working Mac and select Firewire from the list. Verify if there are any signs that the Firewire port is connected to a computer.

If that fails, it highly likely that the power connector and/or logic board are broken.