I found a web page that suggests one can read the .iso images kept on
a disk and use them to do an upgrade without copying them to a cd
first. This is exactly what I want to do.

Here: http://www.linuxquestions.org/questions/history/341506

I've been following the steps outlined there, but ran into a problem
(fairly quickly). Here are the exact steps I took. (The text here
was entered by hand, since I cannot connect the laptop to the network
without switching it to XP due to the firewalls etc. at the palce that
I work. Note, however, that I took these steps just as I composed
this message, so the steps are as complete and accurate as I could
make them.)

I went to my linux laptop and logged in as root.

I created a mount point directory and made it world writeable.

mkdir /mnt/isoxxx
chmod 777 /mnt/isoxxx

I mounted the iso I wanted to read from on this mount point:

mount -o loop /home/CentOs-4.1-i386-bin1of4.iso /mnt/isoxxx

I made that my working directory and checked that the file I wanted to
copy was there.

cd /mnt/isoxxx
ls -la
total 4549
dr-xr-xr-x 2 root root 2040 Jun 11 09:48 ./
....
-r--r--r-- 4 root root 1429017 Jun 11 09:44 vmlinuz

I then tried to copy the file vmlinuz to where I wanted it (on my boot
partition):

cp vmlinuz /boot/iso-vmlinuz
cp: reading: vmlinuz: Input/output error

Since, that failed, I tried just cat'ing the file:
cat vmlinuz
cat: vmlinuz: Input/output error

I don't know why the contents of the .iso file could be unreadable in
this fashion (and what this rather non-descriptive error message is
trying to tell me). Note, that I have no problem reading and writing
to the partition which contains the .iso file that I mounted.

(I have the feeling that the reason I couldn't make a bootable cd is
related to being unable to read from this .iso file when mounted as a
partition.)

What step should I take next??? For example, how do I calculate the
checksum on the .iso file and compare it to what it should be? Maybe
the inital download of the file was botched.

Thanks,
-Chris