Forgot yo give the address (between old age and chemotherapy, Getting old is
not for wimps!)
http://www.ubuntu.com/download/ubuntu/download

Go to System > Administration > Software sources and see if the CD-ROM
option has been set. If so, unset it and try again. How it may have
got set in the first place, though, I don't know.

That was it. I don't know how the CD got added to the mix either, but
once I removed it, the install went OK.

Many thanks. Now I know where to look if something like this happens again.

Sounds unusual to me! I have my doubts...

They could be wanting to send you THERE SPECIAL MODIFIED version of Ubuntu.
Modified to send them all your personal info on your computer and
correspondence.

This is where I would get a new version from and it can be ISOed on a CD.

Are you refering to the fellow that posted his atempt at
performing a update was requesting installation media? As someone
else mentioned, this usually happens when the cd/DVD line in
sources.list is uncommented. That line needs to be recommended or
deleted. I don't see any reason for getting a new iso and reinstalling.

I'm the OP in question. I did manage to run Update Manager for part of
the updates, so I now know which ones wanted the DVD.

Those were:

build-essential
DKMS
libalgorithm-diff-perl (new install)
libalgorithm-merge-perl (new install)

I am not planning on reinstalling, as I want to remain at 10.04 LTS
until 11.04 has been out for a while. And I have no plans to install
10.10, which is the DVD that is being requested.

These may be on the disk and it may be set to use the disk in your sources
as previously mentioned. If that is the case, then it will ask for the CD
in preference to downloading from the repositories. By changing to sources
and deselecting using the CD you can avoid this message. I have found that
using the CD is only helpful at the beginning because as packages get
upgraded the CD versio0n falls behind and needs to be upgraded anyway.

Build-essential includes a bunch of packages that are necessary from
compiling source code. Some apps such as VMWare or VirtualBox may require
them as part of their dependencies since it needs to compile modules to work
with the kernel. DKMS is similar as it works to compile kernel modules
dynamically. I am not sure what the perl modules are used for, but most libs
are dependencies for other packages.

Will there be any more Austin Powers movies?

Go to Update Manager. Click the Settings Button. Click Ubuntu Software tab.
Make sure you haven't selected the disc in the pane at the bottom of the window,