I have changed the name on
/etc/hosts but the top right corner display name won't change
How can i change that name?
Changing your username just to get a different name displayed is not recommended. To make your actual name to be displayed instead of your username, open a Terminal and run:
(taken from fluteflute's answer)
To change your actual username (which defaults to your username), go to System -> Administration -> Users and Groups. Select your user and click the "Change..." button after your current name. Enter whatever you like and press OK to save it. You'll need to re-login to make the name change take effect.