To get the Lego driver to work when using the Windows XP SP3 operating system, you must go to the Lego website to install the driver. Click on http://mindstorms.lego.com/Support/Updates/ or paste the link in your browser window to get to that page. Once there, go to the MINDSTORMS NXT Driver v1.02 (the 4th on the page) and download the driver here. They have updated the driver to be compatible with SP3.