Hi Jessie,
Unless it's a hardware error that needs repair you can try to do what's called a "hard reset".
You do this by removing everything from the computer so it is like it was when you took it out of the box when you bought it.
Also remove the battery.
Now, hold down the power key of the computer for 40 seconds.
Then, once you've done that, reconnect only the AC power and try to turn on your computer like you normally would.
Please let me know how it works.