I was having the exact same issue on a Windows XP SP3 computer at my house. My other PC's also running XP had no issues with the update. I had tried uninstalling from the control panel and rebooting with no luck. System Restore also wouldn't fix the issue. It just would error out. Then I ran the steps Maurice mentioned that included the utility cleanup and that was the fix my computer needed. The utility cleaned up some stray files that prevented the reinstall from running properly. I put in the Pro ID and Key and I'm back in business!!! Thanks for the help..........