Questions about: cleanup

Question: I have upgraded the kernel on my Ubuntu many times in the past. Now I would like to uninstall unused old kernel images to save some disk space. What is the easiest way to uninstall earlier versions of the Linux kernel on Ubuntu? In Ubuntu e
After I add a user using adduser, I can’t see it via System->Administration->Users and Groups unless I logout and then login again. Is that normal? Also, can I set a newly added user as a sudoer or do I have to change that only after adding it?