Synthetickiller
Intel C2Q does not work 24/7 stable near 500MHz FSB, forget about !
Max stable FSB is 450-470MHz maybe, but this will require some voltage tweaking.

As for those 500+ you may seen, they are screen-shot only runs, not 24/7 stable.
Set your FSB to 400, memory to 1000MHz, it will work happily.