Well, I don't have the exact problem, but I can tell you about my experiences with the XFi Notebook and Vista. I have Vista ultimate 64-bit and an HP dv9000 notebook.
What I would suggest 1st is to completely uninstall any creative drivers in the control panel - programs and features area. TAKE OUT THE XFi card. Now reboot and then download the latest driver from creative and install it, follow instructions and then shut down the computer completely (do not restart). INSERT XFi and power on with the xFI card inserted. See if that works.
I have had some very strange problems - not with installing but after installing. For example when I start Vista and then insert the xFi card after it is booted, I'll sometimes get a very high pitch squealing sound when playing music. Also if I hibernate or go to standby with the xfi card inserted it will get stuck in an endless loop rebooting when i try to resume. It does not seem to be completely plug and play for me.
I have found my only solution is to boot from complete shut down with the X-Fi card inserted at boot time to eliminate these problems. That is my experience, I don't know if it will help with your specific problem but I thought I'd mention it.
