Re: Vista drivers...
Check your manufacturer's website. For instance, Logitech has lots of Vista drivers, Dell is slowly breaking them out, Nvidia and ATI are all set, other vendors are good to go, while others are slacking big time.
Also, note that Zone Alarm has nothing for Vista yet, Trend Micro does, other malware protection companies are kind of hit or miss.
Best to do your homework beforehand. Do the research specific to your devices, video cards, etc., before you load it.
As for loading XP Pro over Vista, you're talking about formatting your hard drive and doing a clean install.
Just my .02