I'm progressing in a Sitecore installation on a Dev laptop.
SQL Server up-and-running, able to login as Sitecore / ..... to whom I gave Sysadmin.
So far, OK.
But the SIM connection string:
Data Source=MYMACHINE\MSSQLSERVER;Initial Catalog=master;User ID=AAAA;Password=BBBB
"A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was 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)
Note that it's finding the SQL Server instance I believe, because if I intentionally wrong the instance name, it produces a different:
26 - Error Locating Server/Instance Specified