Configure foreign host for PostgreSQL 8.0.3 on WindowsXP

Installed PostgreSQL 8.0.3 on WindowsXP. Have not been able to configure so
that a client program running on a different WindowsXP box can connect to
the PostgreSQL database.

As I understand the documentation, at least one of the following
configurations should work, but none do. What have I done wrong and how can
I configure so that a connection can be successfully made?

1) The postgresql.conf file has (with everything else being the installation
default values):

listen_addresses = '*'

2) None of the following configurations of the pg_hba.conf file worked (the
program runs on 192.168.2.120 <http://192.168.2.120>):

# IPv4 local connections:
#host all all 127.0.0.1/32 <http://127.0.0.1/32> md5
host all all 192.168.2.120/24 <http://192.168.2.120/24> md5

# IPv4 local connections:
#host all all 127.0.0.1/32 <http://127.0.0.1/32> md5
host all all 192.168.2.120 <http://192.168.2.120>
255.255.255.255<http://255.255.255.255>md5

# IPv4 local connections:
host all all 127.0.0.1/32 <http://127.0.0.1/32> md5
host all all 192.168.2.120/24 <http://192.168.2.120/24> md5

# IPv4 local connections:
host all all 127.0.0.1/32 <http://127.0.0.1/32> md5
host all all 192.168.2.120 <http://192.168.2.120>
255.255.255.255<http://255.255.255.255>md5

I have a Symantec personal firewall installed which I turned off during
testing.

The program runs fine on localhost.

Am using the Npgsql .NET library. The Npgsql.Npgsql.Open() call throws an
exception, the error text of which is "System.Net.Sockets.SocketException:
NO connection could be made because the target machine actively refused it."