Many new Ubuntu users spend hours in look up for settings to change default Ubuntu programs. For example: Suppose you want to change default video player from ‘Movie Player’ to ‘VLC Player’. For setting up default running programs in Ubuntu 12.04, first thing you need to do is click the settings icon present on the top left corner and select ‘System Settings’ option.
Now from ‘System Settings’ page scroll down to ‘ System’ sub section and click ‘Details’ icon.
From left navigation sidebar, the two options ‘Default Applications’ & ‘Removable Media’ lets you change the default programs. ‘Default Applications’ allows you to set defaults for Web, Mail, Calender, Music, Video, Photos whereas ‘Removable Media’ lets you change defaults for DVD, CD and music, photos etc in removable media like USB sticks, CDs & DVDs etc.