How do I associate a custom MIME-type to my local application in the major browsers?

I want to invent a new mime-type and associate it to a custom application in the browser to enable users to launch my app from a web page. The users of my secure web site are in a closed-environment, meaning this is not a general-purpose, mainstream application - I can configure their browser ahead of time.

Spoon.net does something very similar to enable launching virtualized applications using their mini-kernel plugin.

One of the answers to this question alluded to this method, without details for how to accomplish it.

How do I achieve this in a cross-platform manner on Chrome and IE 8/9? Is there a way to do the mime-type association through browser extensions, either native or through crossrider? How does an app like Adobe Reader or Apple Quicktime achieve this? I want to avoid touching the registry if possible.

What are the risks associated with this method? My site is an intranet web application secured with a certificate and trusted by my users. Any reason I should not go down this path?

EDIT: Apparently this can be achieved in Firefox by manipulating the mimeTypes.rdf file.

EDIT: It looks like JDIC is a Java-based mechanism that could be used for the same thing. Is there a similar non-Java construct? Maybe in Javascript?

Solution

It looks like it can be done via a registry change on windows.

[HKEY_CLASSES_ROOT\.atom]
    @="atom_file"

[HKEY_CLASSES_ROOT\atom_file]
    @="Atom Syndication Program"

[HKEY_CLASSES_ROOT\atom_file\shell]

[HKEY_CLASSES_ROOT\atom_file\shell\open]

[HKEY_CLASSES_ROOT\atom_file\shell\open\command]
    @="\"C:\\AtomHandler\\handle.exe\" %1"

[HKEY_CLASSES_ROOT\MIME\Database\Content Type\application/atom+xml]
    "Extension"=".atom"