If you have an Enterprise copy of Office XP then I recommend you do the
following:
1. Create an administrative installation of Office.
2. Install Office onto your clients from the administrative installation.
Since the product key was used to create the administrative installation you
will not be prompted for the product key during the client installations.
However, if you have a Retail copy of Office XP then you really cannot
"deploy" a product key during the installation. If you use the same product
key for multiple installations then you will encounter activation issues.
Hope this helps.