If you a Word 2007 document with docx file extension and you want to open that file in Word 2003 or Word XP, here’s the trick:
Download the Office compatibility pack that lets Word 2003 open and save files in Office Open XML docx format.
Else you can use the free docx2doc service that convert docx to doc files in the browser.
The third option is to mail the file to koolwire and it will convert docx to pdf that you can read inside Adobe Reader.