Vista - Changing Default Protocol for HTTP/HTTPS

OK, this is very annoying. Our office uses firefox, and I can go in and set
it as default browser and in Set Association, I can set it as the default for
all web related extentions. BUT, when it comes to protocols (HTTP, HTTPS, at
the bottom of the page in Set Associations), When you hit change Programs,
ONLY IE is listed there and your are not able to change it to anything else
(or at least by any means I could see).So what does this mean? For up, any
link we send or recieve in Outlook, if clicked on, brings up IE instead of
fire fox. Firefox is still set as default.

How can I change this protocol? This seems rather annoying! Am I missing
something simple?

Thanks
Ken