In a recent discussion the following error raised its head: “If I choose localhost\SQLEXPRESS for the server\instance setting it's fine. But if I use localhost\MSSQLSERVER it throws an error: Error connecting to database localhost\MSSQLSERVER. A network-related or instance-specific error occured while establishing a connection to SQL Server. The server was not found or is not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 25 - Connection string is not valid)”

So the question is really, what can I specify when the TFS Integration Tools installation prompts me with the following dialog:

Answer

Assuming we have a local machine (server) on which we have SQL Server Express and SQL Server installed, a remote database server with SQL Server installed and are in the process of installing TFS Integration Tools.

Which SQL Server?	Example
SQL Express on local machine	localhost\SQLExpress
SQL Server Default instance on local machine	localhost or . (dot)
SQL Server Default instance on remote machine	ServerName, i.e. RangerHost, whereby it could also be the name of the local server, in which case it will connect to default instance on the local server.
SQL Server Named instance on local machine	LocalHost\Instance Name, i.e. localhost\TestInstance or .\Instance Name, i.e. .\TestInstance
SQL Server Named instance on remote machine	Server Name\Instance Name, i.e. RangerHost\TestInstance, whereby it could also be the name of the local server, in which case it will connect to named instance on the local server.