Microsoft Office System reached the Top 1 place in Top Selling Software for the year 2007. CNET says that

office

Microsoft Office Word 2007 helps you produce professional-looking documents by providing a comprehensive set of tools for creating and formatting your document in the new Microsoft Office Fluent user interface. Rich review, commenting, and comparison capabilities help you quickly gather and manage feedback from colleagues. Advanced data integration ensures that documents stay connected to important sources of business information.

To see more top selling sofware visit CNET. :)