How to change the file:// protocol application

Anyone have any ideas on how to change the application that is launched when the pointer is something like file://c:\temp\fred.html ? One of the desktops at work has Firebird installed as their browser and when we use teamcalendar in outlook, the web page opens in Firebird (which won't work due to ocx problems). I need to open it in Internet Explorer. Internet Explorer HAS been set as the default web browser, and http:// web pages come up in ie ok. file ones insist on launching in firebird. the file types option in Explorer doesn't seem to handle the file:// option so I can't work out what I need to change.