If ever you had trouble opening the following file types:
- .docx
- .xlsx
- .pptx
This simply means you are not yet running Microsoft Office 2007 and is probably still running MS Office 2003 or lower. And isn’t in frustrating knowing that your old Office cannot open these files and you think you have to buy the new Office 2007 package?
Actually you can still open MS Office 2007 files with these file extension in Office 2003 using the Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats. If you need a copy, you will need some update packs and simply download the compatibility pack here. No more problems in opening .docx, .xlsx and .pptx anymore. 
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December 21st, 2007 at 5:05 pm
Users (Mac and P.C.) that do not own Microsoft Office, or users of earlier versions of Microsoft Office that are not covered by Microsoft compatibility pack, but still want to open and use Word 2007 DOCX or Excel 2007 XLSX files, can use “docxconverter 2.0″ to convert and open docx and xlsx files. See this.
March 4th, 2009 at 6:03 pm
For a more versatile tool for various formats, I learned about this from Alicia of PsPrint: http://www.zamzar.com/