>>>>>SQL Server is just a servce. You can stop it from Service Manager. or from SQL Server Configuration Manager.
>>>>>If SQL Server Configuration Manager is not in your Start menu go to Windows\System32 forlder and find it.
>>>>
>>>>First, thank you. How do I find which service to stop? you see, I have both SQL Server 2008 running on this PC and SQL Server 2014 Express running on this PC.
>>>>When I open the SQL Server Configuration Manager, I see SQLEXPRESS and MSSQLSERVER running. However, when I log into the SSMS, I see DMITRY2013 (when I try to use SQL 2008) and I see DMITRY\SQL_2014_EXPRESS when I am using SQL 2014. I want to be sure I stop the right service.
>>>
>>>How do you connect to SQL Server?
>>>What is your connection string?
>>>You use only Server=DMITRY2013
>>>or
>>>Server=DMITRY2013\SQL_2014_EXPRESS
>>
>>Yes, my connection string has Server = "DMITRY2013"
>>
>>UPDATE. But as I wrote before, the SQL Configuration Manager only has SQLEXPRESS or MSSQLSERVER (not the name of the server in my connection string)
>
>
>MSSQLSERVER
>is what you need to stop. This is the default instance.

This is very good! I stopped this service and now I can't execute any t-SQL in SSMS. So, this should allow me to test my connection.
Thank you!!!