xp/ vista info

I am in the market for an inexpensive laptop for my wife. She knows nothing about computing. I know a little, not much. But anyway she will only be using the computer for possibly games and emails. However I have heard that the Microsoft Vista has had many problems. Can a new laptop be purchased with XP installed instead of Vista? Also what is XPS?

Any suggestions on a reasonably priced laptop for this kind of use? Make & model would help also. Thank you.