Backup file for the .QDF file, the primary data format used by Quicken, a personal finance software; contains saved accounts, transactions, portfolios, and balance information. To restore these backup files in Quicken, go to File ? Backup and Restore ? Restore from Backup File , then look for the backup file you need to restore (will have the QDF-BACKUP extension), open the file you'd like to restore (a "Restore from backup file" window should appear), then determine a location on your local hard drive where you'd like to save the data file.