Just purchased a techno isel 24" x 19" with kress 800w motor. The unit has not been used much but is a 1997 or so year model with a centronics plug. Anyone know if I can upgrade to regular parallel or usb without too much $$$. I got mastercam 6 with it and it gets a "can't find SIM" error message. What is that? I cannot find in the book what a SIM is...or where to get it...