Finally, my school decided to install Linux on every PC and mostly without windows and partitions with various mightily.
Also because it was useless, use Windows to program with BlueJ and do some spreadsheet with OpenOffice.
Unfortunately, my user is limited 
applicazzioni and therefore can not install, upgrade and customize my own way
Well, so we see how to reset the password for super user "root".
In Linux, there is a startup mode, termed "single user mode" that allows access to the operating system as root without the need to specify a password. 
This procedure works on all Debian systems, or who have the grub installed. (Ubuntu and derivatives ...)
Well, let's see how to start mode Single User Mode.
The first thing to do is restart your PC, press ESC and the GRUB screen appears.
If there is a menu item "recovery mode" select it and press "b" to access the system in "single-user".
If the menu item "recovery mode" does not exist, proceed as follows:
- Select the default boot configuration, and press "e" to edit it.
- Now, select the line that begins with "kernel" and press "e".
- Posizioniamoci end of the line and add the parameter "single".
- We enter to save the configuration and press "b" to access the system in "single user".
Now that we're in the single user mode, we will have root privileges ..
At this point we can reset / delete the passwords of all users of the system through the command:
passwd nomeutente
obviously without the need to know the old password.
Now, reboot and enjoy 
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