Hi. I think i know what the problem is. The newer computers do have a serial port, but they are mostly of the time installed with an automatic modem device that arranges the port in and out traffic. PLEASE correct me if im wrong, people, but i think this is a main issue to people who use a brand new computer with a new serial port.
I had the same problem, and therefore i ordered an SIO2USB interface, im sure that will work fine.
I dont know if the USB interface is compatible with USB 3.0 yet, because im new at this site, but thats no problem for me yet, because i have 2.0 USB ports anyway.
I hope this helps you, and other people aswell.
Regards,
Wolf.