>I've used PortQry, on 1433 and 1434, and the results are:
>
>TCP Port 1433: listening
>UDP Port 1433: not listening
>TCP Port 1434: not listening
>UDP Port 1434: not listening


In SSMS, if you look at the Current SQL Server Log under Management/SQL Server Logs, you should see entries stating "Server is listening on" followed by IP protocol name and a port number. Do you see something like that? If not, the server is not using TCP/IP.

As far as firewalls go, if these machine are on an internal network, shut off the firewall on the machine running SQLExpress (at least while troubleshooting). Check A/V and make sure it doesn't have a firewall running as well.