The following example demonstrates the procedure for emptying a file so that it can be removed from the database. For the purposes of this example, a data file is first created and it is assumed that the file contains data.

http://msdn2.microsoft.com/en-us/library/ms189493.aspx

USE AdventureWorks;
GO
-- Create a data file and assume it contains data.
ALTER DATABASE AdventureWorks
ADD FILE (
    NAME = Test1data,
    FILENAME = 'C:\t1data.ndf',
    SIZE = 5MB
    );
GO
-- Empty the data file.
DBCC SHRINKFILE ('Test1data', EMPTYFILE);
GO
-- Remove the data file from the database.
ALTER DATABASE AdventureWorks
REMOVE FILE Test1data;
GO