We had a different serial adapter and cable with the mac, it was a mac one that I couldn't get to work with Windows. So I bought a USB to serial cable, Prolific chip and driver, that I think installed fine, the system says the driver is installed and it is working. Yes I wondered about the other settings, the flow control on the USB port is set to none, and the same in Signblazer, the Bits per sec, 9600, data: 8 bit, Parity none, Stop bits: 1. Its running on Comm 1 - through the prolific USB port (Comm 1 was the only install option apart from LPT in the Graphtec Driver, I so I installed on Comm 1); I thought maybe there's some other setting I'm missing, or some test I can do which could find the fault. The cutter is on HP-GL, but it seems to receive nothing. That said, before the cable had the correct driver installed the cutter came up with an I/O error when I sent data, with the driver installed it no longer comes up with that, so I think data is getting through ... do people have more luck with the ieee 1284 parallel port? I could try that next if I get another cable.