The primary filegroup cannot be backed up as a file backup (4042599)

Full File and Filegroup backups fail with the following error message

"The primary filegroup cannot be backed up as a file backup because the database is using the SIMPLE recovery model. Consider taking a partial backup by specifying READ_WRITE_FILEGROUPS."

Under "Simple" recovery model in SQL Server 2005/2008, the Full File and Filegroup backups are restricted to read-only secondary filegroups.

There are a number of resolutions to this problem:

1. Modify the selection set to include only secondary filegroups for the Simple Recovery Model databases
2. Select the Partial Database or Differential Partial Database backup type.
3. Modify the recovery model of the database to "Full" or "Bulk Logged".