I have a CD with Ubuntu 10.10 and a laptop with Ubuntu 8.10. The laptop had all sorts of crud on it, and anything I wanted to keep was backed up on an external drive, so I was happy to do a wipe and reinstall instead of an update. So after a bit of faffing about trying to work out how to get the thing to boot from the CD drive, I did that.
So the screen comes up with the choice: the options are Try Ubuntu and Install Ubuntu. I choose to install and to overwrite my current installation. So far so good. I then get a progress bar labelled something like copying files (I forget the exact wording) and further options to fill in for my location, keyboard locale, username and password. On each of these screens there are forward and back buttons. On the last screen (password), the forward button is greyed out. Well, I think to myself, no doubt it will become active when that copying files progress bar completes.
The progress bar never completes. It hangs. And the label changes from copying files to the chirpy ready when you are. The forward button remains greyed out. The back button is as unhelpful as you'd expect it to be. And there's nothing else to click. We have reached an impasse.
I tried restarting the laptop, to test whether it actually was properly installed. It wasn't. I tried to run Ubuntu live from the CD, to test whether the disk was damaged. That wouldn't work either, but I suspect it's just because the laptop is old and has a slow disk drive. I'm typing this question on another computer using the Ubuntu live CD and it's working fine. So there's nothing wrong with the CD.