Check the online Product Page for Windows XP downlaods for your system. Kind of doubt Gateway would bother to put XP drivers for a notebook issued with Vista 64. Downgrade from Vista 64 to Windows XP? I'm getting the impression living a Rock and Roll fantasy is not all it's cracked up to be.
You should check out gateway's website to make sure they offer your hardware's drivers for XP. As long as you have the drivers, necessary system requirements, and the OS disc, you can.