keithlm :
Unless you have a specific application or piece of old hardware that will not work with Vista then there is no reason to downgrade.
What, apart from the fact that Vista is inferior to XP unless you have a lot of CPU power and memory to throw at it? Every Vista machine I have ever owned or been in charge of I've dumped in favour of XP because it was just so slow. They've all been put up to Windows 7 now.
If we're talking about Windows 7 to XP then yes I'd agree, but Vista just blows.
As far as drivers go, OP, just download everything you need and be done with it so you can be sure that everything on your system is accounted for. If you can't get certain things, I strongly recommend Driver Agent to find them for you - it does cost but it's a tiny sum for a year of amazing driver finding - never let me down.