For KDE :"The KDE Control Center"
http://docs.kde.org/development/en/k...omponents.html
Component Chooser
The component chooser allows you to select the default applications you would like to use for various services. Here you can define what Email Client, Embedded Text Editor, Instant Messenger, Terminal Emulator and Web Browser to use. If you prefer to use Xterm, Vim or Mozilla, this is the place to specify those preferences.
File Associations
This is where you configure everything to do with file associations. Here you can select a filetype, and choose what applications you would like to be able to open it with. You can also select which icon you would like to represent each filetype, and whether to show it in an embedded or a separate viewer.
"Starting Files With Programs: Setting MIME Types"
http://www.debian.org/doc/manuals/us...-mtdyo.en.html