It was, I think, a half-arsed attempt to keep up with the promises they made much, much too early on in the development cycle. They should have fessed up and taken their lumps for breaking that promise rather than releasing Vista which, inasmuch as it is an improvement over XP in certain ways, is not the be-all/end-all improvement over XP that it should have been - it really should have been released as XP service pack 3.
if VISTA was released as XP service pack 3 there would have been rioting at microsoft headquarters
VISTA was all new, written friom the ground up, and a piece of crap.
& is beter, but it is just XP to me with everything moved around so yu cant find it.