Possible Duplicate:
Cannot connect to SQL Server
I had SQL Server 2008 functional before I installed Active Directory and setup a domain (this is on Server 2008 R2, the only domain controller), but now I can't login to the SQL Server (from SQL Server Management Studio). It says:
Cannot connect to (local).
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: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) (Microsoft SQL Server, Error: 2)
What's going on? SQL Server 2008 is on the Domain Controller, same server/computer.
Apart from the obvious (don't run application services on a domain controller), you're apparently trying to connect via a Named Pipe - why ?
Enable TCP/IP connections in the SQL Server Configuration Manager console and use a Domain Administrator to log on to SQL server specifically via TCP/IP.
(Only Domain Administrators can log on to a Domain Controller)