Microsoft today released a free combo VHD edition of Windows Vista and Office 2007 Professional which includes Publisher, Excel, Outlook, Outlook, PowerPoint, Access, and Word.
You can download this all-in-one package from Microsoft Download Center and run it on your Windows XP computer without making any modifications by using the free Microsoft Virtual PC software.
Start the Virtual PC software and just open the Windows Vista cum Office 2007 image - the software will run independent of your existing XP SP2 setup and will not alter or install anything on the computer.
Excited ? There's a small catch - though the Office 2007 / Vista image file is free, it is a bit bulky (~2 GB to be exact) and requires addition 10 GB of free hard drive space for running smoothly inside the Virtual PC software.
If you think your Broadband connection can take the load, get the Office 2007 cum Vista installer from microsoft.com/downloads/ (file available in VHD image format).