have
Good processor 64 bit is a must
good graphics card 256 dedicated. 512 ideally
and at least 4gigs of ram. on 4gigs vista uses half its resources. But bare in mind xp was also a memory hog when it came out. And its a memory hog so it can be quicker on loading applications. actually im at 37% resources. But as soon as i install adobe cs4 and some other things it will be around 45-50%
EDIT the most important thing to running vista is this
Download Windows tune up utilities 2009. Its the best way to tweak vista