Raise the FSB and tighten the timings. You'll probably want to make sure that your RAM is in sync with your FSB.
edit: Yes, I realise now that I just told him to run the ram at a higher clockspeed than it was intended for, which is the definition of overclcoking.
Lower the CPU multiplier if you have too, and bump the voltage if it get unstable. Check your overclock with memtest86.