Yes, but now when they have to purchase new machines, they will be more willing to jump to Vista instead of sticking with XP. I have many clients that still request XP even on new machines because of Vista's issues. However, now that SP1 is coming, it will be easier to persuade them to switch.
Microsoft is happy to make that decision for them, for everyone in fact. OEMs must stop selling Windows XP computers on June 30th.
