You are not giving us much of a clue.
What machine - lathe, mill etc have you got, what drivers and more important - what laptop.
When this project first started, the output to the machine was via the parallel port - LPT1, principally because this port was faster, and could keep up with the fast response needed for a CNC system. The system could support a serial port for some of the slower responses.
I run my system from a laptop - but I am lucky - my Toshiba laptop has a parallel printer port - and runs from a 5 volt system. A lot of modern laptops have no LPT1 and only a 3.5 volt system.
What output have you got from the USB - is it USB2 - how does it fan out. To drive the various stepper motors and switches you need about 16 outputs and maybe 8 inputs - so you need a 24 port card, that is as fast as the old LPT1.