Vista is full of problems. There are only 4% users worldwide, 37% XP, 44% W7 as at August 1st.
By the way, Windows 8 is a total flop, same as Vista but for a different reason. No learned person or company wants to go near it. It's at 5.4% users worldwide after its one year old release! GARTNER predicted it wouldn't go beyond 6% in its full existence because it doesn't buy you anything. It just complicates things.
Some XP users will stick with that system for a few years more, those who move up will switch to W7.