go to your main page  and select site  Actions > under Look and Feel
select > Title, Icon, Description. change  the title  and save. This
will change the bread crumb for the entire site.

MOSS does NOT work like 2003. The title  bar displays the path of the
file, not what is put into title or description through site  settings.
You can change  the title of some pages  (depending on the template) by
using the publishing bar  that appears when editing the page. On the far
left, click on the page  button and choose Page settings. This is
different from what you get under Site Actions. Changing the name under
this Page settings  area will make it change on the title bar but you
have to do it to every page you create  (and only the top page of a site;
pages under that don't let you do it).

We are looking into a way to do this programmatically because manual
changes to every page simply won't be possible. Some templates don't
have a Page Settings button so you are stuck with path names instead of
titles. We're a fairly small farm - I can't imagine how a large farm
is handling this.