using a windows vista, would be the stupidest thing ever ! use linux or windows xp.. know it only register 3 gb ram, but my 5x wows only take 2,3 and i am able to use 3,4 before it reaches it limit.. and xp only eats up the 300 Mb ram, were vista uses 1 gb... Xp and linux will aswell be improving your perfomence A LOT, would guess:

XP = 10-20 %
linux= 15-40 %