I'm trying to remove LXDE from my 12.04 system.
I've tried running the following commands (as root from a terminal):

apt-get remove lxde
apt-get purge lxde
apt-get autoremove

I've also tried a rather lengthy command that was linked to from another question.

However, when I log in, LXDE is still presented as an environment choice, and it still functions perfectly well, as if I've done nothing.

I ran the above commands again, but got the following message:

package . . . is not installed, so not removed.

So, where do I go from here, short of re-installing Ubuntu and all my programs?