Your problem is not with Query Analyzer. If you block that, you still have to worry about people making connections through MS Access, the OSQL command line utility, or other methods. If you are really concerned about this, you can change your server so that it only allows NT security connections. At the moment, your server is likely in "mixed security" mode.
Regardless, you should be able to modify the SQL Server account for the user and either delete it or restrict it's access.
Thanks Blindman, I know my problem is with the SQL Server configuration. The main problem is that there is a client application that it uses a SQL Server user and it can be disabled without modifying the client, that's why the server is in Mixed mode, but I don't want Developers enter to the production environment with that user.
It would be like a temp fix disabling the SQL Query Analizer, of course if there is a way.
You can't control database access through Query Analyzer. Consider that even if there is a Query Analyzer option that disabled SQL Server logins, you would have to enforce this on every copy of Query Analyzer and you'd have no way to prevent users from changing it back.
Are you concerned about users modifying data through Query Analyzer, or just about them modifiying the database schema? Make sure the login does not have permission to modify the database schema (the application shouldn't require this in order to function), and then if you need data security then Application Security roles are the way to go.
Thanks for your comments. My concern is that developers modify data using the query analizer, it looks like Application Roles is the way to go but since the developers have the source code they would know the Application password to activate the role, well I think I could create a COM Object in the server to make the connection, so developers don't have access to the password of the role.