Quote - On a 64bit sytem, more cores is the easier way to greater overall render speed.  But on a 32bit system, all the cores must share a limited amount of RAM, so you quickly reach the point of diminishing returns.
If you didn't specify a 64bit system when you bought the computer, it is probably 32bit.  Mouse down to the lower left of the screen to the Start button, and follow Start/control panel/system and it show pop up a window which details what OS you have.  In XP, you'll see a plain text window;  in Vista, a graphic window.  See link above for an example;  when you see no reference to 32bit or 64bit, it is 32bit.

Well yes I have XP now (that doesn't even come in 64bit does it?) So if I'm understanding you right, to get the full potential of the quad core you need 64bit. But if f I can only afford to upgrade one thing though (for now) is it better to get the processor first or upgrade to Vista 64bit first?