From Mandriva Community Wiki

[edit] Changing Preferred Applications

Usually from a KDE desktop changing preferred applications settings. Open the KDE Control Center, and browse to "Components: File Associations".

However, some programs may be "gnome-open" to launch files, and defaults need to adjusted a different way.

For example, Installing Rhythmbox in Mandriva 2006 makes Rhythmbox the default player for many music types, and Thunderbird uses "gnome-open" to launch WAV file attachments. You may want to undo some of these changes. From a KDE desktop, there no easy way to access these preferences.

As root, you can edit "/usr/share/applications/defaults.list"

Search for rhythmbox.desktop to find the entries it added, and delete or change them as needed.

This file is consulted by the "gnome-open" program when it decides what application to select open a provided file.