How to reconfigure the graphic interface in Ubuntu 13.04

Trying to fix a problem with my touchpad, I screw up the graphic interface. I am not sure what I did to the core files of the system, but once I reboot the system, it didn't show anything at all... Black page with a blinky pointer on it. 

So, first, I had to reboot again and right before it goes to black again, press Ctrl+Alt+F2 (that would take you to the command console). Set the login and password. 

Make sure everything is on the lastest version, so type:

sudo apt-get update && sudo apt-get upgrade

After this, you have 2 options. The thing is that this version of Ubuntu comes with a display manager called lightdm. You could remove all the files and reinstall it, or install a new one (which is also very common) named gmd. I will explain both (although it is almost the same process).

Installing Gdm
1. I made sure Gdm wasn't installed before (or with damaged packages)

sudo apt-get remove gdm

sudo apt-get purge gmd

sudo apt-get install gmd 

2. I removed all the xserver.xorg also, to reinstall them again

sudo apt-get remove --purge xserver-xorg

sudo apt-get install xserver-xorg

 3. Reboot the system or start gdm

sudo reboot 

or

sudo start gdm 

Installing (or reinstalling) LightDm
1. Type in the console

sudo apt-get remove lightdm

sudo apt-get install lightdm

sudo dpkg-reconfigure lightdm

At this point, a window will show up to select one of the two display managers. Pick one of the two, and now reboot or start one of the two from the console.

That worked for me!