Limited use XP

I have a laptop that had trial version of Office 2007. When it expired I wanted to revert back to XP Small Business. I have uninstalled and reinstalled XP a couple of times but still get the same error. The activation window comes up and stays up saying "Please wait while the wizard initiates..." but nothing more happens. When I close the window all office programs have limited access just like 2007 trial. I can't type anything new on the document or spreadsheet, even Outlook acts the same. Any ideas what the problem is and what I can do?