I am new here. I was facing issues with emacs-snapshot sourced from a PPA, so I tried following these instructions (blindly =/), and
sudo apt-get remove `apt-cache search emacs | awk '{print $1}'` --purge
took out a big chunk of Ubuntu 12.04 including Software Center, System Settings and probably a few other things that I am not immediately missing. I was able to install Software Center back with which I tried to install System Settings unsuccessfully (it tried to install the KDE version).
Does anyone know how I can get System Settings back without reinstalling Ubuntu?
PS: I am also missing the clock on the top-right which is usually next to the menu button containing shutdown/display/etc. settings.