Have the people you are emailing to got 'Microsoft Word'? Also, are you using 'Outlook Express'. I was having a similar problem, but from the other side of the coin. People were sending me 'Word' documents and others were sending emails using 'Outlook'. I don't use either! These are the things you need to know before making any alterations to your PC.
It is possible for the recipient of 'Word' documents to download and install 'Word Reader' but that is if they want to? If you are using 'Outlook' and the recipients are using a different email client, then their email client has to be set up to accept emails from 'Outlook'.