I'm trying to map a single table from asp.net simple membership into my model. but when the DB is being updated by OA its trying to recreate the simple membership table, which i want to try and prevent
I assume that you are using the visual designer. OpenAccess provides two options for updating the database in its Update Database from Model wizard - "Create Database" and "Migrate Database". In your case you should pick "Update Database" and then you are able to select which tables to be updated. You may deselect the table you quoted and then OpenAccess will not try to create or update it. Please see the attachment for an example.
If you have more questions about updating the database, please do not hesitate to contact us for help.