Hello! I am new to this forum and a nubie to MS SQL

I installed SQL Server 2008 R2 standard edition version 10.50.1600.1 in February of 2013, but never used it because other software packages I installed used their own SQL Server instances, typically SQL 2005 express. Now it is time to install software that will use MS SQL and I find that I can't connect to it to do any necessary configuration. SQL Server Management studio can connect to the instance of SQL 2005 express.  

MS SQL 2008 R2 is running under the 64 bit version of MS Server 2008 R2 [RTM], SP1, Ver 6.1 (7601). I have 24GB of memory in a fast ASUS server.

The server is the single domain controller. I know, not recommended, but I don't want to add another server to the domain. 

I checked SQL server configuration manager and found all services running with the logon as the domain server's administrator account (DSAA). The running services are: SQL Server (MSSQLSERVER), SQL Server Agent (MSSQLSERVER), SQL Server Browser, SQL Server Reporting services, SQL Full-text fiiter Daemon Launcher (MSSQLSERVER), SQL Server Analysis Services (default) and SQL Server Integration Services 10.0.  The protocols (shared memory, named pipes and TCP/IP) are all enabled. The same protocols are enabled for the clients. 

The logon that I thought I used for SQL Management Studio is also the DSAA. I say "that I thought I used because that is what is in my notes from 2013.

Despite the fact that the services seem to start using the DSAA logon, when I try to log on to management studio I get this error message:

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) (.Net SqlClient Data Provider)

Also, when I  look at the logs for any recent date, the following error recurs with a frequency of 1 minute after initial housekeeping:

Error: 18456, Severity: 14, State: 11

Login failed for user '<domain>\<DSAA name>'. Reason: Token based server access validation failed with an infrastructure error. Check for previous errors. [CLIENT: <local machine>]

My authentication mode is "mixed" and my database name is 'master'

Any help that can be provided is much appreciated.

It is possible that your administrator password has changed in the windows level.

Create a new user and add to local admin group 

configure your services to use this new account and restart.

They try to log in it might help.

YOu can also try with your sa password if you remember.

<domain>\<DSAA name check right  and DB-owner to user.

• Go to Start | Run and then type "dsa.msc".  That command will open the Active Directory Users and Computers console.

Next right click on the active directory group in the console and click on "Find". Type the service account namein the find dialog box and click on the "Find Now" button.

Right click on the service account name from the search result --> Select Properties --> Go to Account tab. Here you have to check whether account is locked out or expired or disabled in domain or needs the password changed.

Hi

States 11 & 12 mean that SQL Server was able to authenticate you, but weren't able to validate with the underlying Windows permissions. It could be that the Windows login has no profile or that permissions could not be checked due to UAC. Try running SSMS as administrator and/or disabling UAC. Another reason could be that the domain controller could not be reached.

Refer to to the below link for more information on Error states. http://sqlblog.com/blogs/aaron_bertrand/archive/2011/01/14/sql-server-v-next-denali-additional-states-for-error-18456.aspx