IMHO where most Windows users are running into problems is trying to use Vista...a very processor/graphics/ram intensive OS on 3 and 4 year old systems.
I'd be willing to bet a lot of the systems are early Pentium 4 (1.5 - 2.0 ghz) systems with 512 of ram and 64mb video cards.
Vista it seems needs a LOT more than that to run.
I saw the same kind of problem when I worked at Best Buy and people were going from Win 95 to XP.
Vista is going to force people to either see the light and buy a Mac

or scrap their current systems and buy brand new machines so that Vista runs properly.