stream converter precidence

[DigDug]

I've been playing around with converting Filestreams of directory's to
XHTML instead of HTML like FF does currently. I have a streamconverter
written and running, but I can't figure out how to make the browser use
it instead of the default one. Does anyone know the best way to do
this? Do I have to write a new content handler and then force the
conversion inside there, or can I just get the browser to use my
converter without doing so much extra work (perhaps by removing the old
converter)?