sqlserver-php5.3，IIS7sqlsrv链接错误

-49:This extension requires either the Microsoft SQL Server 2008 Native Client (SP1 or later) or the Microsoft SQL Server 2008 R2 Native Client ODBC Driver to communicate with SQL Server. Neither of those ODBC Drivers are currently installed. Access the following URL to download the Microsoft SQL Server 2008 R2 Native Client ODBC driver for x86: http://go.microsoft.com/fwlink/?LinkId=1637120:[Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified

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-49:This extension requires either the Microsoft SQL Server 2008 Native Client (SP1 or later) or the Microsoft SQL Server 2008 R2 Native Client ODBC Driver to communicate with SQL Server. Neither of those ODBC Drivers are currently installed. Access the following URL to download the Microsoft SQL Server 2008 R2 Native Client ODBC driver for x86: http://go.microsoft.com/fwlink/?LinkId=1637120:[Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified

http://msdn.microsoft.com/en-us/sqlserver/ff658533