Enable User Instances in SQL Server

in VS when using wizard to create database in SQL server Express edition sometimes it will show

Generating user instances in SQL Server is disabled. Use sp_configure 'user instances enabled' to generate user instances.

solution :
Open the SQL Server Management Studio Express. This is the downloadable program in the same site where you downloaded the SQL Server 2005 express used to manage SQL Server 2005 Express.
In the query editor type this text: exec sp_configure 'user instances enabled', 1.
Then type: Reconfigure.
Then restart the SQL Server database.
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