"There are no visible restrictions for ports in Windows-2000-server, but
they exists (as we seen)."
This is true.
In that case, check your postgresql.conf config file for the
listen_interfaces parameter, and check it is set to * (i.e.
listen_interfaces = *). Then restart the PostgreSQL service if you've
had to change it.
Also check your pg_hba.conf, for the "ipv4" lines.
Andy