Setting Default System Theme

[moe]

What file contains the default system theme? I mean, when you add a new user, 
they get that theme automatically instead of Bluecurve.

I've changed a number of files, but they don't do the trick:
/etc/gtk-2.0/gtkrc
/etc/skel/.gtkrc
/etc/gconf/schemas/desktop_gnome_interface.schemas
/etc/gconf/schemas/metacity.schemas
/usr/share/themes/Default/gtk/gtkrc

Anyone? :)

Thanks,

-Jeff