tm Even though the clock speed might be a bit slower the fact that the 9100 has either a dual core processor or has hyperthreading (neither of which really means 2 cpu - kinda like this - dual core can think about 2 things at the same time instead of just one and hyperthreading is a way to do that with only one core) means that it should outperform the 4600. The memory is really only a factor if you find that you are using it all. I no longer recall exactly how to monitor those things on xp (vista and 7 have little gadget programs for doing that) but if all you are doing is folding then the 9100 with smp should go faster and get you more points

You could find some benchmark program that you could run on each and driectly compare the results if you wanted to know for sure lol