PC Stats tries to find the sweet spot for RAM on Vista.  Trying 512MB, 1, 2 and 4GB they see just what you can get away with, and if the 4GB helps you out.  Gaming and productivity software will start to respond a lot better if you can keep Vista happy.
“Do you need as much memory when you’re running office applications as you do when you’re gaming? How much memory do you need in Vista to game comfortably, and spreadsheet smoothly? Usually a hardware upgrade isn’t required for a new operating system. Yet if you are planing to upgrade Microsoft Windows XP to Microsoft Windows Vista, it’s almost impossible to avoid a PC overhaul. If the PC doesn’t have enough RAM to satisfy Vista’s intense thirst, you’ll be the slowest thing on two wheels.”

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