Hopefully you had a /home/?

If so, you can reinstall an OS, while keeping everything under /home/.
i.e. your Desktop, Firefox settings, downloads, etc.

Wow, it's looking more and more like 8.04 is Ubuntu's Vista! When I
first saw Vista, I could see that Linux had the door opened away from
Windows, but Ubuntu "upgrade" is stumbling badly here. Just like has
been said about MS, more and more Ubuntu users are going to "just say
NO" to "upgrades".

Not sure if Ubuntu prompts you on installation, requesting if you want
to keep all of the files in /home as MEPIS does on installation.