Your instructions solved my problem. Thanks. Rather than /etc/rcx.d, however, I needed /etc/init.d. As this directory contained no script, I used the "touch" command to create a file called "ndiswrapper.sh". Once I had created this file, I could use your second reply to modify this file.
I believe I am coming to understanding (ever so gradually) the way the Linux filesystem works. It is most gratifying to find help when I need it, from people who understand this system.