Turn OFF xfire balloon popups by:
0) Start up xfire & login
1) Tools -> Options...
2) Under "General" tab, at bottom, in the "Balloon Tooltips" pane:
Uncheck both boxes.
3) If you ALSO want to turn off the sounds xfire alerts with:
Select the "Sounds" tab & uncheck whatever/everything.
4) Select the "OK" button to save all your setting changes.