Hi,

The previous version of the Excel rendering extension, compatible with Microsoft Excel 2003, is renamed to Excel 2003. Only the Excel rendering extension is available by default. You must update the Reporting Services configuration files to make the Excel 2003 rendering extension available. The content type of files generated by this renderer is application/vnd.ms-excel and the file name extension of files is .xls. This renderer provides backwards compatibility with Microsoft Excel 2003. To use the Excel renderer instead of the earlier Excel 2003 renderer, install the Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint.

But the Microsoft Excel 2003 rendering extension is deprecated. The features are still available in the release in which they are deprecated; however the features are scheduled to be removed in a future release of SQL Server. Deprecated features should not be used in new applications.The Reporting Services BIFF8 rendering extensions Reporting Services reports to the Microsoft Word and Microsoft Excel 1997-2003 binary interchange file format. SQL Server 2012 includes extensions that render in the Microsoft Office 2007-2010 Open XML format.

For more information, see

http://msdn.microsoft.com/en-us/library/dd255234.aspx

Deprecated Features in SQL Server Reporting Services in SQL Server 2012.