Nautilus, other file managers, and default file manager

[kareemy <kareemy gmail com>]

Hello,

I switch my desktop environment between gnome, xfce, and windowmaker
constantly. When I am not using GNOME I do not want Nautilus to be my
default file manager.

Specifically, Firefox loads the default file manager when you click
the "Show Folder" button in the Downloads Preferences. So when I am in
Xfce and click Show Folder, Nautilus loads up and takes over my
desktop. Firefox claims it is just running the default file manager. I
have looked everywhere and cannot find out how to change the default
file manager

How do I change the default file manager to either nothing or xffm
when I'm not using gnome?

Thanks,
Kareem