DIET (at least as of version 2.1.11) uses SQL Server db library (ntwdblib.dll) to connect to SQL Server databases. As of SQL Server 2005, this library is no longer shipped with the database engine.

Additional Information:
Although the SQL Server 2005 Database Engine still supports connections from existing applications using the DB-Library and Embedded SQL APIs, it does not include the files or documentation needed to do programming work on applications that use these APIs. A future version of the SQL Server Database Engine will drop support for connections from DB-Library or Embedded SQL applications. Do not use DB-Library or Embedded SQL to develop new applications. Remove any dependencies on either DB-Library or Embedded SQL when modifying existing applications. Instead of these APIs, use the SQLClient namespace or an API such as OLE DB or ODBC. SQL Server 2005 does not include the DB-Library DLL required to run these applications. To run DB-Library or Embedded SQL applications you must have available the DB-Library DLL from SQL Server version 6.5, SQL Server 7.0, or SQL Server 2000.

We are investigating alternative APIs for communicating with SQL Server 2005 databases.

The current workaround is to copy the ntwdblib.dll into a directory in your path, or to the same directory where the diet.exe application resides.

If you do not have this DLL, it can be downloaded here:
http://www.dovetailsoftware.com/download/ntwdblib/ntwdblib.zip

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