I wanted to try out different desktop environments so I installed XFCE, KDE, GNOME, etc on top of Unity in Ubuntu 12.04

After a while I decided that I didn't like those other DEs and would stick to Unity. So I changed my default DE to Unity by configuring gdm.

> sudo dpkg-reconfigure gdm

Now I am able to choose my DE at login time and all of DEs are working properly.

But the strange thing is that my boot up screen says 'lubuntu', my login screen is KDE, and my desktop is Unity.

How and why is this happening? Why didn't my gdm configuration have any effect? Does login and boot up screen need to be configured separately from the DE?

There are other similar questions here but they are not the same as this one. I do not want to remove the other enviroments I'm quite happy with having a list of DEs to select from. I want to know how to set proper defaults.