DSB,
You can not directly control the motors from your laptop, you will need a stepper or servo driver to interface with the motors. A relatively cheap and good system is this one
http://www.siderealtechnology.com/
user group on yahoo
http://tech.groups.yahoo.com/group/sitechservo/
I am using this system for my G-11 mount. Other than a computer you can also use a Argo Navis DSC to control the Servo system.
The stellercat system called the Servocat is also tried and tested system, but i think the Sitech is every bit as good if not better.