The standard procedure for a notebook that doesn't turn on after confirming the AC adapter works is to:
1. Disassemble the notebook.
2. Disconnect everything. You should be left with the motherboard, a CPU, a heatsink, and 1 stick of memory.
3. Connect it to AC power and an external monitor.
4. See if it boots.
5. If no boot, take out the BIOS battery, unplug it, and let it sit for a while.
6. If still no POST, then the board or the CPU is dead, and require replacing. Oftentimes (>95%) it's the board over the CPU, but there's no way to tell.