My team is currently running SPS 2003 on one server. All of the site
creation is hard-coding the server address like so:

http://server:xxxx/sites/designsites/zzzz

This is happening in a lot of other areas as well. this is not
allowing users to login to the sharepoint from home, or if they do
have the IP address, not allowing them to access certain files that
are hard-coded back to the server, breaking the pages. Can someone
tell me how to change this so the name of the server itself does not
come up? Is there a central variable control that can change this
from the top-level down and update all the html in a site collection?

Or a specific way to find all the instances of the files on the
server that reference the server in this way and then change all the
files to reference /sites/designsites/etc....