Taking SQL Server to Single user mode and resetting passwords

From the command prompt type: SQLServr.Exe –m (or SQLServr.exe –f)

Goto C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\Binn

SQLCMD –S <Server_Name\Instance_Name>

CREATE LOGIN test with PASSWORD=’test’
go
SP_ADDSRVROLEMEMBER 'test','SYSADMIN'

SP_ADDSRVROLEMEMBER ‘test’,’SYSADMIN

http://timradney.com/2013/11/21/how-to-reset-the-sa-password-in-sql-server/