None, provided you do the following;

Documents created in 2007 will not be recognised by 2003 by default. Consequently you wont be able to open your shopping list for example if you created it in word 2007.

You'll notice that a word document created in 2007 will have a .docx extension as opposed to .doc (as default).

The free download of Office Compatibility pack will remedy this problem and allow you read 2007 work with 2003.

http://www.microsoft.com/downloads/d...displaylang=en

You won;t have any other issues, other than reconfuring your outlook etc.

Its not uncommon to do this, many people can't click with the new 'ribbon' look and are reluctant to move onto 2007. Myself included!

Ben.