So is there no natural key in your Access table, something like create_date or order_number? If not, how about adding an extra column and populating that with an ascending number sequence? Then you can import to a staging table on the SQL Server and insert to your main table from there.

Better still, take this opportunity to start using the relational database as it was intended, and create a "proper" key rather than the somewhat arbitrary order of insertion or physical storage.

John