Ok! I'm a relative newbie and I'm pushing 80 so be gentle with me? I'm running Ubuntu 8.10 quite happily, but often I install an application via Synaptic. It downloads and installs - then NOTHING! It just disappears. Where do these things go? Occasionally, if I'm lucky they do appear listed in one of the application sections and work, but all too often they don't. Clearly they are in the box somewhere. I'm puzzled - or more like I'm doing something very WRONG!

There are a couple of possibilities, depending on what you're installing. Programs without a GUI, ie, that run only in the console, generally won't show up in your menu. Programs specific to other desktop environments sometimes have an entry in their configuration that tells them to only show up in that D.E. The executable for most programs are stored in /usr/bin. You can check there to see if they installed. The menu is populated based on files in /usr/share/applications. These are in the format of "name.desktop". They are text files which you can edit. I've used the ones that are in there as a base to create new files for programs without a menu entry. I couldn't find a more user friendly site detailing these files, I'm afraid, but here is this: http://standards.freedesktop.org/desktop-entry-spec/latest/

Just to clarify, a GUI is a Graphical User Interface and a DE is a Desktop Environment. Your Desktop Environment is probably Gnome, just so you know.

Maybe if you give us the name of one of the packages that has seemingly disappeared, we can help you with an example and explicit instructions.