My workstation that has SQL Server 2008 R2 Express for development purposes installed has been moved out of a domain into a Windows workgroup. While being part of the domain I used the account "MyDomain\MyUserName" that had domain admin rights. Now I log in to my computer as "MyComputerName\MyUserName" that has local admin rights.
In the SQL Server Configuration Manager I have changed the account that starts the "SQL Server (Express)" service from "MyDomain\MyUserName" to "MyComputerName\MyUserName".
I can connect with the instance in SQL Server Management Studio (using Windows authentication) and I can see all databases in the Object Explorer in the left side. But once I try to open any database node in the Object Explorer I get a message that access to the database is not possible. I get this message for all databases except system databases like "master" or "tempdb".
If I try to run any query on one of the databases I get a "SQL Server Message 916":
The server principal "MyComputerName\MyUserName" is not able to access the database "MyDatabase" under the current security context.
Is there any way to the get access to my databases again?
I also tried to create a new database manually in SSMS but it throws the error:
CREATE DATABASE permission denied in database 'master' (Microsoft SQL Server, Error: 262)
I forgot to mention that the workstation runs with Windows XP (Service Pack 3) and the domain the workstation has been removed from was an old Windows NT domain - in case this should be important to find the reason for the problem.