To get the root through GUI
1) You have to press
alt + F2
it will open dialog box called 'Run Application'
2) then you type
'gksudo nautilus' without quots
in the text field and then Ubuntu will ask for your Password.
3) type the password
then you will get the window with '/root'
where you have all admin rights
In this mode there won't be any warning when deleting or modifying files which will get you in to trouble even if you accidentally deleted or modified admin files. Therefore be careful and do not use this mode unless otherwise it's really needed.