Prepare Image Type
Use the Prepare Image Type page of the SQL Server Installation Wizard to specify whether to install a new instance of SQL Server 2008 R2, or add features to an existing instance.
Select the radio button that specifies your choice:
Prepare a new instance of SQL Server 2008 R2
Add features to an existing prepared instance of SQL Server 2008 R2
If you select the option to add features to an existing instance, use the drop-down list to select the prepared instance of SQL Server to update.
You can add the SQL Server SysPrep supported features (Database Engine and Reporting Services) to a prepared image of SQL Server. Other features that are not supported by SQL Server SysPrep can only be added after the prepared instance is completed.