Īlso note that many later usb adaptors do not really comply with true rs232. unless you can find one of those tech friendly ones. generally ports 1 and 2 are already mapped, if your using a conventional desktop with an older than 6 year mother board. there are quite a few out there that start way above that ie 6 and higher.
do a bit of homework and try to get an adaptor that uses the lower port numbers ie 1-4 by default 3 or 4 being the highest that is usually mapped (and most desireable ) in many older devices and apps.
which removes some of the critical timings and level detections (application dependant ) the hardware layer to application is far better than later os's which tend to buffer the ports far too much. so have and still use an old lappy (1999) with win98. Part of my issue with 232 has always been the programing of our 'in house' end devices (yes old sckool tech ) and the timings for appropriate handshakes. Have been using usb to serial adaptors for years
