Mess with the power savings in Vista. Customize one of the plans. Set the maximum CPU value to 100%, but set the minimum to something like 50%. You can also adjust the PCIe power saving to something like performance and power saver. Set it to power saver when you're not playing a game or doing anything graphically intensive. Go in there and mess around. You won't screw anything up.
How do you think that your laptop stays fast and cool in Mac OS X? Apple used similar power saving techniques that you can enable in Windows (downclocking the CPU/GPU when it's idle).