If you're attaching a Word 2007 file, then they either need Word 2007 or
they need to have the Office 2007 Compatibility Pack installed.
You can, however, save the file in Word 97-2003 format and then attach it,
and users of older versions of Office should be able to open the file.

Signature
Herb Tyson MS MVP
Author of the Word 2007 Bible
Blog: http://word2007bible.herbtyson.com
Web: http://www.herbtyson.com
> My system is Vista and I have MS Office 2007 When I send a word file as an
> attachment the person that I sent it to can not open even if they have an
> older word version. HELP