Sounds more like hardware error than anything else so I'd suggest
disconnecting the HD and then seeing if the Ubuntu CD's will boot.

If not then try re-seating memory, and if you have more than one
module to try them singly. Basically, hardware fault-finding is a
process of re-seating / exchanging components until you find the
fault. Also worth bearing in mind that SATA and IDE cables can go bad
so worth swapping those too if nothing else works.

FWIW the update was probably coincidental but we'll know more after
the results of the above hardware checks.

Try to mount it with a Puppy Linux Live CD and see if it will read it and
hopefully repair it.

Hey, I had a windoz disc, and it installed that just fine. LOL. Weird
isn't it?

Now that THAT installed, I'm gonna see if I can install Ubuntu in place of
it.

That didn't work. It looks like it flat out won't take any ubuntu discs at
all.

Windoz seems to be working fine though.

Presumably the Windows CD was a pre-recorded one and the Ubuntu ones
are recorded onto CD-R ? That would indicate that the CD drive is
having difficulty reading the CD-R but is OK on pre-recorded. Not that
uncommon and the usual culprit is dust on the CD drive lens that's not
enough to prevent the more reflective pre-recorded discs from reading
but enough to make CD-R ( or any type of disc that's home recorded )
from being read correctly.

Try a CD Lens cleaner - essentially a CD with small brushes glued to
the data layer that sweeps over the lens as the disc spins. Useful to
have one of these anyway for cleaning optical drives !

If that doesn't cure it then the dust can be deeper and not possible
to clean it out, or the laser that does the read/write may be fading,
so a new drive is required. Not expensive these days so not a major
disaster

The alternative would be a bootable USB drive but you'll still be
needing to read CD-R's at some point so worth trying the cleaner then
replacing if necessary.

PS - you may think you've successfully recorded on a drive that has
been affected by dust but the recording is likely faulty.

No, the windoz disc was home made too. I should try booting from a USB
though. That's a great idea, thanks!

Still worth trying the CD lens cleaner as there's evidently something
preventing those Ubuntu discs from reading correctly. It may well be
that when you recorded the Windows CD the drive was working better !!

Did you check the checksum of the disk? I think that is the best way to
make sure the download went well and the disk burned right.