[CentOS] yum list installed - 3rd column

On most of the CentOS 5 machines I manage, if I run "yum list
installed" the third column just says "installed" for all
packages. But on one machine, some lines show instead a repo
name preceded by an @ sign. Apparently the repo from which the
package was installed, which would be immensely useful.

Two questions:

1. Can I have that feature on the other CentOS 5 machines too?
The machine in question has yum version 3.2.27-12.el5_from_el6
while all others have version 3.2.22-39.el5.centos.
Where did that "el5_from_el6" version come from? The "yum list"
entry for yum itself does unfortunately not show a repo name.

2. Can anything be done about the lines still saying only
"installed"? How do find out where those packages came from?

aTdHvAaNnKcSe
Tilman

-- 
Tilman Schmidt
Phoenix Software GmbH
Bonn, Germany