You can use Database Configuration Assistant (DBCA) to delete a database. When DBCA deletes a database, it shuts down the database instance and then deletes all database files. On the Windows platform, it also deletes associated Windows services.
To delete a database using DBCA:
Start DBCA as described in "Starting DBCA".
In the Database Operation window, select Delete Database and click Next.
Select the database to delete and click Next.