Best solution is to not buy and install Vista.
Iam not gona buy it untill it have been out for a year and most problem is solved.
And its not necessary to install Vista if you allready have XP on your comp.
Only reason to get vista is if you buy a new comp. But even there i would choose XP.
Vista is to demanding. It require a high end computer to run smooth and also over 40 gig HD space. And as i have only a 76 gig raptor disc, vista is not going into this comp.
In fact Vista is more or less eyecandy and an security op system. Ive heard rumors that its a pain to enable and maintain all security that comes whit it so most people will not run thos programs, and whit that in mind there is no point to use Vista.
DirectX10 will be optimized for XP as well and i guess most program that will be made are backwards compatible whit XP.
So my tip is. Dont buy it and install it untill at least it have been out on the market for a year. There is really no point to buy it atm.
Just my 2 cents.
Ps: Vista is set for release in Januari 2007. Dont remember exact date but there is a set one.