Based on http://blog.citrix24.com/configure-sql-express-to-accept-remote-connections/.
Ensure that 'Allow remote connections to the server' is ticked
At a command prompt, enter:
netstat -ano | find /i "<process_id>"
The returned records should indicate that the process is now listening on port 1433, e.g.:
On the 'Log On' tab, click 'Start'