My apologizes for confusing a HD serial ATA port with a RS-232 port
:*(. So, to now post more sensibly I will quote Bob Sillett who
created the freeware SWLog (logging/radio control for HF rcvrs)
recommends as follows in his FAQ:

" It is getting more and more difficult to find a computer with a real
serial port. Many times a USB-to-Serial adapter needs to be used. If
you currently have a USB-to-Serial adapter and it works for you, great!
But if you are looking for an adapter, we recommend the IOgear GUC232A
adapter. This adapter works very well and it also fully works with the
Sysinternals Portmon serial monitor tool, which is a great tool for
troubleshooting. Plus the IOgear adapter is only $25 or so and, as of
Winter 2005, can be found in pretty much every Wal-Mart."

Incidentally Sillett's page is:

http://www.shortwavelog.com/default-english.html