The Ultimate Virtual Reality Simulator

Brain: CPU
Eyes: Graphics Processor
Ears: Sound Input/Output(IO)

sensory inputs: anything that effects your body

Shock: Your brain can turn off sensory inputs to negate the intensity of the simulation.

CPU isn't the best choice, but its the closest example. It really is just a super computer with a graphics chip embedded working in tandem with your Eyes(Graphics Input).

The big question:
Where's the user?