>When a table is added to a DBC it is linked with a unique id. One cannot overwrite an old table with a new one by the same name because the ids won't match and the DBC will complain.
>Question: What is the best method to update an EXE of an previously installed app without overwriting the old data tables (hence, the data)?


If it's the EXE you need to update then just overwrite it. If you need to add a new table that you added to the DBC, copy in the table and simply overwrite the DBC. If you are updating a table that already has data in it you write an update app to modify it using ALTER TABLE. HTH