Im not sure if this will completely take care of the problem listed by the OP, bu when i searched Google for "disable outlook in firefox" that thread was the first thing that popped up. I have found out how to change the mailto: action in firefox (3.5.7) to stop outlook from opening. Tools>options>applications find "mailto" in content type column, and click the drop down box in the action column. There you can select from several mail clients including gmail. This same procedure can be used to select which application opens most relivent file types. hope this helps. and sorry if i dug up an old post for no reason.