This is an issue with many users. You received a document from someone and you cannot open the document as it was done in Office Word 2007 or Excel 2007. You only have Office 2003. So how do you open the document to view it? You can download Word Viewer from Microsoft. This will cover Microsoft Word 2000, Word 2002, Office 2003 and Office 2007. Microsoft also created Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats, which you can download and install after you have installed Word Viewer.
Key words for Google search are Microsoft Word Viewer or Excel Viewer.