If don't have Office 2007/2010 installed on your computer and/or you find that the new Office file formats, such as DOCX, XLSX etc. are not shown in the
Documents Tab you may need to install IFilters from Microsoft.
The latest filter pack is available here:
http://www.microsoft.com/downloads/details.aspx?FamilyID=5cd4dcd7-d3e6-4970-875e-aba93459fbee&displaylang=en