nrc1:/var/cache/apt# apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
You might want to run 'apt-get -f install' to correct these.
The following packages have unmet dependencies:
libc6 : Depends: libc-bin (= 2.11.3-3) but 2.13-35 is installed
locales : Depends: glibc-2.13-1 but it is not installable
E: Unmet dependencies. Try using -f.
I had this original Lenny install in use for thin client facility to students
I successfully upgraded it to Squeeze long back
During my leave for five long months, the other guy tried to install some things from Testing and Sid
Now as I'm trying apt-get upgrade
the above is the result
my current sources.list
deb http:// ftp .us.debian.org/debian/ squeeze main contrib non-free
deb http:// ftp .us.debian.org/debian/ squeeze-proposed-updates contrib non-free main
deb http://security.debian.org/ squeeze/updates contrib non-free main
I have no idea how to cope up the machine is in use by nearly 900 students but has all old software

sources.list; what you have done so far and what you're trying to achieve... – sr_ Nov 30 '12 at 13:02aptitude, it's pretty clever with these issues. – sr_ Nov 30 '12 at 14:02apt-get dist-upgrade, that may resolve it. Make sure to actually read what it says its going to do before pressing Y, to make sure it isn't removing a bunch of stuff you want. – derobert Nov 30 '12 at 15:05