The most common causes are:
1) The AC Adapter (charger) died, and isn't providing any power.
2) The DC Jack (the port where you plug the charger into the laptop) is damaged and not properly connected to the motherboard anymore.
3) The motherboard suffered a component level failure
4) The battery suffered a failure and is causing a short.
Basically what I'd try first is unplugging the battery, then plug in the charger and see if the computer works with the battery not in it. Then I'd try a new charger. After that I'd crack open the computer and see if DC Jack is soldered on and possibly broken, or if its a harness type then just unplug it and plug it back in. You can use a multimeter to see if power is getting through the jack too.