while memory size is important, speed is as important. Yes if you have say 360 meg of pc 100 ram, it won't be as nearly as effective as say 160 meg of pc800 ram. Front side bus also plays a huge role, as it is the speed that each component is capable of communicating with each other. Having a high front side bus is extremely vital, this way your uber fast processor isn't getting bogged down by slow communications with other components, or slow components bogging down communications because they can't keep up with the central cpu. I really wouldn't say any part is 'more vital' than others, as it makes up a central whole. Its like having bald tires on a car that has 600 horsepower. The horsepower is useless because the car will not go anywhere if you try to peel out (no grip). So if you have a 1ghz machine and only upgrade the processor to even 3ghz, you won't notice too much difference unless you upgrade other components too. You get the idea 