doc.FAQ.WhatAreTheDifferencesAmongUserSystemAndFileDSNs

• User DSN - User DSNs are available for use only to the user who created it. User DSN connection parameters are stored in the HKEY CURRENT_USER\Software\ODBC\ODBC.INI section of the registry.
  
• System DSN - System DSNs are available for use to any user who logs onto the local system. System DSN connection parameters are stored in the HKEY LOCAL_MACHINE\Software\ODBC\ODBC.INI section of the registry.
  
• File DSN - File DSNs comprise a set of DSN connection parameters that are saved to a text file with a .DSN extension. File DSNs typically appear in C:\Program Files\Common Files\ODBC\Data OpenLink? recommends use of System DSNs whenever possible.