If you can, remove the battery from the laptop and hold the power button for 30 seconds. Then try running the computer w/o the battery. If this works, give it a minute to go through the bootup process, and see if the light is still flashing. If the light is flashing, then it probably is the dead motherboard, or maybe power regulation. If the light is normal, just put your battery back in and see if it works, without the charger. If it is good, drain your battery, (I know, it's not recommended, just do it :D) and then once your battery is drained, plug in, with the LID CLOSED, and the COMPUTER OFF, and let it charge until the light turns green, signaling that the laptop is done.