better yet use synaptic to remove the old kernels and support files
which will also remove them from the start up.

Where are the old kernals listed in synaptic? I found some references
to Linux-image-2.6.24-19-generic and
Linux-ubuntu-modules-2.6.24-19-generic under Base System. Are these the
ones that I should remove?

What is meant by "Base System"? I don't see anything like
that in Synaptic (Add/Remove).

The short answer is Yes. You need only the most recent provided it is working
well. Removing the lines does not remove the packages. You can do this from the
package manager. There is a utility to do this in the repositories called
System-cleaner.

I found package called System-cleaner in Synaptic using Search, but
can't seem to install it. What section is it listed under? I tried
looking under Base System and System Administration but didn't find
System-cleaner.

It was listed in Add/Remove, so I installed it (8.10, which had
been updated from 8.04, and from 7.10 before that). This is the
related blurb:

"system-cleaner-gtk finds and removes cruft from a system.
Cruft is (currently) packages that apt marks as automatically
removable, or that Ubuntu no longer supports.

"Homepage: https://wiki.ubuntu.com/CleanupCruft"

-------------

When installation was finished there was a message to
double-click the icon of a program I wish to run.
Having installed programs but not having been able to
find them without going to a Forum and have someone
who happened to know the previous name of the program
suggest I try running that, I double clicked. Nothing.

OK, run "locate system-cleaner-gtk" and bingo. A file
with that name is here:

/usr/share/app-install/desktop/system-cleaner-gtk.desktop

along with nine hundred thousand other files, one
for every existing program my repositories make
available. Then ls -l to learn it is not executable.

1) What are those files in /usr/share/app-install/desktop?

2) Anyone know how to find if this program was actually
installed and if so how to run it? FWIW "locate cleaner"
turns up nothing else with the word "system" -- only
that enigmatic file among enigmatic files.

I'm beginning to think there may be things about Linux
that I won't find out by pressing the F1 key. Are there
some sort of tablets I could take after each meal to
soften the learning curve?

It should be under System | Administration. I am in KDE 4 now so can't confirm
it. It is sometimes called Cruft Remover. Maybe someone can confirm this as
well.