ERWin 连接SQL Server 2005，仅有2005的客户端是远远不够的，还需要sql server2000的一个连接组件--NTWDBLIB.DLL，版本为8.0。直接copy到System32目录下即可！这个烂问题困扰了我长达2天，终于解决了，贴出来方便大家！

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附：ERWin的Readme中的说明：

7.2 Requirement for Connecting to SQL Server 2005

If you are trying to connect to SQL Server 2005 from a machine that does not have the SQL Server 2000 client installed, you will not be able to connect to SQL Server 2005 using AllFusion ERwin Data Modeler or AllFusion Model Manager. AllFusion ERwin Data Modeler and AllFusion Model Manager require the use of DB-Library for connecting to SQL Server databases. SQL Server 2005 no longer distributes the DB-Library files, though DB-Library is supported for connecting to SQL Server 2005.

In order to be able to connect to SQL Server 2005, the file NTWDBLIB.DLL needs to be installed on your workstation. If you have a SQL Server 2000 installation CD, the SQL Server 2000 client can be installed from the CD by executing sqlredis.exe located on in the \x86\Other folder. If you do not have a SQL Server 2000 installation CD, you will need to contact Microsoft support.