With the launch of Office 2007 Microsoft changed the file extensions of Word, Excel and PowerPoint. The New Extensions added an “x” to the earlier Office File Extensions, thus an ms word 2003 document which earlier had .doc extension, became .docx in the Newer versions of Microsoft Office namely Office 2007 and Office 2010.
Now If You are still using Office 2003 and receive a new Office 2007 or Office 2010 Word or Powerpoint or Excel File then MS Office 2003 will give you an error and you will not be able to open these new Office files.
What to do now? especially since you cannot simply log on to Microsoft's Website to buy Office 2010 just to read 1 attachment or 1 presentation.
Here is a simple solution by which you can convert Microsoft Office 2007 Word, (docx), Powerpoint (pptx) and Excel files easily to older Office Versions so that you can open them in your MS Office software.
Just Log on to Zoho Viewer and convert MS Office 2007 files easily to Older formats, the best part about zoho viewer is that No Sign Up is Required and you can convert many file formats like Microsoft Office: doc, docx, xls, xlsx, ppt, pptx, pps; OpenDocument: odt, ods, odp; OpenOffice:sxw, sxc, sxi; Other Formats: rtf, txt, html, csv, tsv easily online.