ok. If you have a stock computer from dell or hp, w/e with only 1 or 2 gb of ram and a dual core 2.4 say. You should get xp because if requires less ram. Now if you have 4 gb and want the vista features ( such as a free windows 7 upgrade) then get vista. I have a powerful enough comp to run vista but I choose not to because of the fact that my computer loads in about 25 to 35 sec compared to the 1 min vista requires.