I have a computer with an AMD Athlon 64 3000+ processor 2ghz but apparently gets rated at 3ghz or somewhere around there performance. 1.5gb ram. XP, Vista or 7. which would be a suitable choice for max performance of not just ram, but processor. I plan to upgrade to 3gb ram eventually. Now from this it is an older model motherboard. You may be wondering why even ask the question. If the choice is XP, would it be Pro or Pro 64. Any help would be appreciated.