Well find us your motherboard that your getting or if your keeping your old one then we can find some good ram for you.
See your mobo might only support 400mhz ram, and for like £40 you can get a mobo that supports 800mhz plus the newer Dual core CPU's
As for overclocking... a cpu is set to a certain speed which say yours is 3.0 GHz, it is actually more capable of say 3.4GHz, but it will overheat, so you need a whopping cpu cooler so sit on the top of it.
Kev
