You remove a table from a data dictionary by selecting the table you want to remove from the TABLES node of the corresponding data dictionary connection and pressing the Delete key. Removing a table from a data dictionary frees the table, but does not delete it. If you want to erase a table that you have removed from the data dictionary in this way, you can do so by manually deleting the table's files from the directory (using Windows Explorer, for example).
You can also use the SQL DROP TABLE statement to remove a table from a data dictionary. This approach both removes the table from the dictionary and deletes it permanently.
CAUTION: There is a utility called FREEADT.EXE that can be used to free tables from a data dictionary. (This utility is located in the same directory as the Advantage Data Architect executable.) This utility should normally only be used when a data dictionary has been deleted, but the associated tables are still marked as bound to a database.