I'm using Ubuntu 12.04. I don't know what happened to my Unity and Unity 2D, but it doesn't work anymore, only Gnome Classic does (When I try to start using Gnome-Shell, the session starts with Gnome Classic). So when I log in using Unity, The only things I see are Desktop wallpaper and icons (I think Nautilus is working fine) but no launcher and no panel...
The fact that Gnome Classic is launched instead of Gnome-Shell made think that there is a problem with my GPU proprietary driver; though, I don't know from where to open the propritary drivers manager through Gnome Classic.
So what I want to do now is to completely reinstall Ubuntu without losing my personal folder. Actually, I've already seen this choice when I was upgrading 11.10 to 12.04, now it doesn't exist.
I should add, my home folder contains more than 50GB of files, so the online backup tools won't help.