While I agree that the hard drive is the prime suspect, it is very possible that other parts have come loose.
If you have the knowledge to do so, you could check the internal parts and connectors.
With power off and the power supply disconnected, remove the battery and open the bottom cover to expose the memory and hard drive.
Oh, listen closely as you flip the unit over to make sure you don't hear little parts tumbling around inside the unit. If you hear little parts rattling inside, it is time to take the unit to a service center so they can identify the parts and make a repair. Do not open the case if you hear parts rattling. If you loose the loose parts, the service center will have a harder time identifying which parts broke loose.
Make sure that the memory is securely seated and the the hard drive is fully mated with it's connectors.
Can you see the cooling fan? make sure it was not damaged and spins freely. Make sure the fan power connector did not pop off.
As many laptops have socketed CPUs, it may be worth the time to have someone make sure that the CPU is secure in the socket and has no damaged pins.
Chas