Installing another de / wm

I installed Mageia 2 with KDE. A few weeks ago I installed the desktop environment / window manager called "Enlightenment" however, I was unable to customise Enlightenment because Mageia will not allow me to log in as root or even to customise whilst logged in as a normal user.
I would like to replace KDE with a lighter desktop but if Mageia will not allow me to customise a second desktop then if I replaced KDE I am worried that I will no longer customise any other desktop I replace it with.
Why doesn't Mageia allow its users to log in as root?
I would like to replace KDE with a lighter desktop but if Mageia will not allow me to customise a second desktop then if I replaced KDE I am worried that I will no longer customise any other desktop I replace it with.
Why doesn't Mageia allow its users to log in as root?