If you are not un UNIX and running "du" command, you need a software to analyze your hard disk and see which are bigger file on you computer and smaller. I will show you two free tools who make your work easer for this argument.
The first one is TreeSize Free.
The Ubuntu 8.04 release candidate brings you the latest and greatest GNOME 2.22.1 with lots of new features and improvements, such as a new version of the Nautilus file manager that uses the faster and more reliable GVFS backend and shows a list of possible actions upon insertion of removable media, an international clock applet that can show time and weather information for multiple locations around the world, the new Seahorse keyring manager, and Google Calendar support in Evolution.