I need a new computer to play games on what should i get?

i was looking at alien ware area-51 7500. The problem is i read from numerous people that alienware is overpriced but they never gave an alternative. Also is windows vista really as bad as people say and should i demand windows xp? If alienware is overpriced, what has the specs of alienware with a reduced price? Also please don just tell me to build my own because i honestly dont know how to build a computer so thats out of the question.