If all you need is a driver update ( rather than more powerful graphics card ) then why not update now, even if you will not upgrade to Vista. Will not cause any problems and is good housekeeping anyway.
my graphics card is a radeion x300.idont play games on my pc so seems ok.i looked on the ati website.and i noticed there is a vista driver for my card.should i download this driver now?.or wait till i have upgraded to vista.i like the sound of the home premium.
I updated the drivers on my PC which were XP and vista compliant, you will need to see if the drivers work for both OSs. If not then it will have to be afterwards.
Did the upgrade advisor say you will need to do it or it would be done automatically? The advisor said for me that my TV card would need updating (by me) but in fact when Vista is installed it goes online as part of the process and downloads available drivers so in the end my TV card was updated automatically.