In response to customer demand, computer manufacturers pressured
Microsoft into offering an easier way for users to “downgrade” their
new machines.
Business customers who feel that Vista is too bloated and slow, or who
find it doesn’t run what they need it to run, now can get Vista taken
off, and XP put in its place. Meanwhile, Fujitsu, Lenovo, and
HP have joined Dell in offering new machines with XP installed instead
of Vista.
(source)