I don't know if it can help you, but you could try a virtual machine...... google for "Microsoft Virtual PC 2007", it is a free download....... install that on Vista, and then create a virtual machine in it into which you can install Windows XP (or Linux or whatever you wish). It doesn't support all hardware but your device might work - i for instance got my scanner working that way which is 7 years old and there's no drivers for it for Vista either. if you still have your XP CD it only cost you an hour's time to install it and a few 100 MB of hard drive space - if it doesn't work, just delete the virtual machine file and you have that space back It's a lot easier than setting up a dual-boot system and safer too - even a virus can execute happily in the guest OS and you can watch it melt down your hard drive - it won't destroy anything really as that is a virtual hard drive made of only a file, and if you have that backed up, you'll be running again in a few seconds
Even if your hardware does NOT work, it's still a great way of still-using software that won't work under Vista (various video converters!!!) I'm on Vista Ultimate too and baffled by just how much trouble there is with video codecs.... however slap XP into a virtual machine and all your troubles in that respect are gone, you're not watching or converting video all the time and if you do, just take an additional minute to boot XP right inside Vista and enjoy all codecs that you can find...... just make sure you got enough RAM for the activity, and don't run any CPU intensive tasks in Vista itself while being active in the guest OS. Great software that one, from Microsoft, and best of all, FREE.