Using the Web Platform Installer to set up a development server, but it insists on using .\SQLExpress as the database server.

I'm using SQL Server (12.0.2000), but it doesn't provide any way to change the DB server; this is preventing me from installing DNN

(I tried following the steps for deploying the Zip file instead, but that won't connect to SQL Server either despite a valid connection string in Web.config)