Problem

You have backup a database on SQL Server 2005. Then, you try to restore the backup file on an existing database and receive the error message below: Restore failed for Server ‘SQL Server name‘. (Microsoft.SqlServer.Smo) Additional information: System.Data.SqlClient.SqlError: The backup set holds a backup of a database other than the existing ‘dbName‘ database.
(Microsoft.SqlServer.Smo)

Meaning Of Error

This error message indicates that you are going to restore a database on another database which are not the same database. For example, you have backup Northwind database and try to restore the backup to Adventure works database, the error will occur.

Solution

To solve the problem, you can use the overwrite the existing database option while you're restoring.
1. On Restore Database , select Options tab on the left menu. Then, check Overwrite the existing database on Restore options.
Note: This option will overwrite any existing data on the targeted database.
2. Try to restore the database, the problem should be gone now.

Conclusion

Hope the error will be fixed.