Sql Server Name and restoring databases

Hi, We have to restore a database from a dead Win2k3 server. We can re-attach the databases just fine, but our software calls to Server=subdomain.example.com;Database=soandso;

When I install SQL Server (2005) on the new server, it wants to name it MACHINENAME\SQLEXPRESS. How can we set up SQL Server on the new machine to use "subdomain.example.com" instead or to keep the software compatible?