Originally posted by: ScrewFace
What kind of PS do you have and what is its wattage? To overclock your great card increase the memory core by 10Mhz increments until you start seeing artifacting and then lower by 5MHz until the artifacting stops. After you have found your maximum memory overclock increase the core clock the same way until you get a hard freeze and then back off by 5Mhz increments until the game plays smoothly.
Use 3DMark2001 SE's 'Nature' benchmark to do this as it's very good to test out your overclock.
I hope I have been some help to you. Take care.