Try this first:
1. Remove the battery and AC cord. Remove the bottom cover/covers of your laptop.
2. Remove and reseat your RAM modules.
3. Replace your covers.
4. Hold down your power button for 1 minute (Battery and AC still disconnected).
5. Replace your AC power (not battery) and turn on.
This is called a hard reset. If it works COOL, then replace your battery. If not then remove your HDD and try starting your laptop.