You can clean up the SpellQuizzer database by deleting orphaned words that you do not plan to use again. This is done from the Database tab of the Options screen. Click the "Specify Orphan Words to Delete from Database" button to bring up the Delete Orphaned Words screen. If there are no orphaned words in the database a message will be displayed stating so. Once you have the Delete Orphaned Words screen open you will see a list of orphaned words. Simply check the boxes beside the words you wish to delete and then click the OK button.
Note: There is no harm in leaving orphaned words in the database. In fact, it can be helpful to leave them there in case you wish to add them to future spelling lists you create. The only real reason for deleting them is that it can help to reduce the space taken up by the database on the hard drive if space is a concern.