A final note on this thread--I tried re-installing Debian because during the first installation I remembered seeing messages about not being able to find the package.cd files. It turned out that when I used the scan option it found the ones for "main" and "contrib," but not the ones for "non-free," "non-US," or "local." (So I guess they're optional, and maybe available only from a download???) And it never prompted me to insert the second disk. When I tried to switch disks the CD drawer wouldn't open. (This has never happened before. I guess the installation procedure ties up the device somehow?)
Anyway, I bought the CD's from Cheapbytes. They're a set of four: two binary and two source. The two binary CD's seem to be almost duplicates of each other. (#1 has tools, #2 has FAQ's, plus other seemingly minor differences.) The Linux that I installed works OK (from my extremely limited perspective as a total newcomer!). So I'm wondering: what's the reason for that second disk? (When I installed I tried both options: install from a CD or from a CD set. Neither prompted for a second CD.) Peter