Problems getting mach3 to work with a certain computer are common.
Mach3 with the parallel port driver will not work on windows 7 64 bit at all. You can stop trying. What type of computer are you using with XP? Laptop,desktop? Some laptops need work to get them going, other laptops simply will not work. What is your kernel speed set to in mach? What are your acceleration, velocity and steps per inch set to in mach? You should reduce the accel and velocity to the minimum to make sure they are not too high. Are there LED's on your breakout board so you can diagnose which pins are being controlled with mach?