Controlling an electrical motor with my laptop
For the brushless motor you would like to control you need:


Motor itself (needless to say but still)
Electronic speed control unit for brushless (ESC)


Most of the time ESC can be controlled via PWM, so you need micro controller which will feed that ESC with pwm. In your case 0%, 50%, 100%, but ESC pwm is used for RC models and have range of 13% duty cycle for 0 to 20% duty cycle for 100%. It is calculated from 20ms pulse which is feed to RC input and 1.5ms-2ms range.


Microcontroller 
I suggest you take Arduino as it is easiest to find examples on net for RC/PWM.


Of course you need power supply...