Symptom: You receive the following error when trying to drop an orphaned user from a msSQL database.

The database principal owns a schema in the database, and cannot be dropped. (Microsoft SQL Server, Error: 15421)

Solution: Follow the steps below:

1. Open up Microsoft SQL Server Management Studio
   1. Start->All Programs->Microsoft SQL Server 2008 R2->SQL Server Management Studio
2. Navigate to the database that you cannot drop the user from.
3. Expand the Security section inside of the database
4. Expand the Users section and right click on the user and rename it (to something other than the new user... assuming you are trying to use a new login with the same username)
5. Expand the Roles section underneeth the Security section
6. Expand the Database Roles section
7. For each Database Role, Right click->Properties on a role and ensure the Owner attribute is set to the new account you wish to use
8. Once you have removed all references to the orphaned account inside of the Owner attributes, you should be able to remove the user from the database.