VSTO2005 beta redistributable package is the most recent update to the VSTO redistributable runtime and includes everything you need to run applications developed using the .NET Framework and Microsoft Office Word 2003 and Microsoft Office Excel 2003.
Microsoft Visual Studio Tools for the Microsoft Office System is the technology that brings the power and productivity of Visual Studio .NET and the .NET Framework to business solutions built on Microsoft Word 2003, Microsoft Excel 2003 and Microsoft InfoPath 2003.