If you are storing this file in another location, then save it as a non-hidden file (without the prefix), and make sure that the ODBCINSTINI environment variable specifies the location.
This was in preparation for using Microsoft Access as a front-end tool for a SQL Server 2005 database.
You can rename the table in Access after linking and the link will not be broken.
However, there will be some minor ramifications in doing so when it comes to using the Microsoft Linked Table Manager which will be highlighted in a future tip.
In a nutshell, you are being asked for the primary key for the table.
If you are privy to this information please select the correct field because performance depends on it.