Back in the days of Dos and Windows 95/98/ME, when programs could directly access ports, the pins of the parallel port could be toggle to drive a stepper motor. Normally only 4 pins were required for a standard stepper motor. In the old days, timer0 could be used to control the time intervals, but now Pentiums include a high speed timer that could be used instead.
For Windows NT/2000/XP/Vista, you'd need a driver that provided an interface to control the motor.
You didn't specify how the PC interfaces to the motor.