There are many different approaches to this. Here are some of them from the head. 1. You can use a microcontroller like Arduino.
2. You can use the serial port and socket. There will be a good resource here if you want to continue this route. http://www.easysw.com/~mike/serial/serial.html
3. If you only need to control two motors, you can use the headphone jack on your computer. You can connect a simple amplifier circuit to each left and right speaker line. Then connect each of the amplifiers to a separate motor. Then you can write a program that generates a separate sound for each channel, thus changing the voltage indicated by each motor.
PS, if you use a servo, you can control the exact angle of the laser.