I know that there are dozens of threads about this but none seem to come to a conclusion, it is really frustrating. I can't pick between XP pro SP2 and Vista Business 64 bit SP1. I just got a brand new Mac Book Pro- 2.4 Cpu, 8600 GT 256 MB. I am PLANNING to uprgade to 4 gigabytes of ram. Am I correct in saying that I need 64 bit vista to utilize the 4 gig of ram and dual core? I'm sitting here and my mind constantly changes, 1 second I know I'm getting xp, the next I read a comment on the forum and I think, oh no no, i need vista. 90% of the reason for me using Windows is for playing games. I plan on playing Flight Simulator X, COD4, and Crysis, thats it. Thats why I am really feeling like I want to have DX10 ability from Vista. Is DX10 worth the possible loss of performance from Vista? I don't care about losing ~5-10 fps but I want it to be playable and decent/nice graphics. I really wish windows would make this easier instead of being moneymongers. It is making me mad simply not knowing which to pick. I would really appreciate just one honest, no-biased, recommendation that will leave me happiest.