How to: Prevent Automatic Startup of an Instance of SQL Server (SQL Server Configuration Manager)
During setup, Microsoft SQL Server is normally configured to start automatically. You can change that setting at any time.
To prevent automatic startup of an instance of SQL Server
On the Start menu, point to All Programs, point to Microsoft SQL Server 2008, point to Configuration Tools, and then click SQL Server Configuration Manager.
In SQL Server Configuration Manager, expand Services, and then click SQL Server.
In the details pane, right-click MSSQLServer, and then click Properties.
In the SQL Server <instancename> Properties dialog box, in the Properties box, set the value of Start Mode to Manual.
Click OK to close the SQL Server <instancename> Properties dialog box, and then close SQL Server Configuration Manager.