The following links will download free viewers which will allow you to open and read documents from others without buying the originating program:

The following link will download a free office suite which is for all practical purposes the same as the Microsoft Office modules, including Access, Excel, Power Point and Word.  OpenOffice is free, but they format and run the same:

The following link will take you to a Microsoft web page where you can download a free Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats. By installing the Compatibility Pack in addition to Microsoft Office 2000, Office XP, or Office 2003, you will be able to open, edit, and save files using the file formats new to Word (.docx), Excel (.xlsx), and PowerPoint 2007. The Compatibility Pack can also be used in conjunction with the Microsoft Office Word Viewer 2003, Excel Viewer 2003, and PowerPoint Viewer 2003 to view files saved in these new formats. For more information about the Compatibility Pack, see Knowledge Base article 924074 . Users of the Microsoft Office XP and 2003 programs Word, Excel, or PowerPoint— please install all High-Priority updates from Microsoft Update before downloading the Compatibility Pack.