Hi ,

Stop all the services related to SQL. Eg: SQL server,Agent,Analysis,Integration etc.

Got to Command promt.

Type as :

Step 1 : net stop mssqlserver

Step 2 : net start mssqlserver /f /T3608

Mssqlserver is your Instancename.

Once the Services started , type SQLCMD to check the connectivity as a single user mode.

Hope it will help you.