Radeonator, Powerstrip, RivaTuner, and Rage3D Tweak will all do that I believe.... But I would suggest that once you find a "comfortable" speed, that you look in to modding the current BIOS on your video card and reflashing it with the higher speeds so you don't need the software mod anymore. Mine is BIOS flashed to 360/340 and works flawlessly but its watercooled so your mileage may vary. Good luck and be careful. Most of the memory I have seen on these on stock cards craps out between 350 and 370 and the cores between 360-400, depending on the cooling. 340 Core and Memory is a good starting point. Try that first and play some games and run some loops of 3DMark looking closely for any artifacting. That is your first sign of stress/heat. If all is well you can go up 5Mhz at a time, but I wouldn't recommend running the memory long term over 350Mhz if you do alot of gaming. Nothing like being in the middle of a frag match and crashing back to the desktop. An all stock card will usually do 340/340 all day long with no problems, but all cards are not created equal...heh. Good luck and be careful. Better slow and playing than fast and RMA'ing!:lol:
Ooops...my bad.. Maybe I should have put it in really big letters instead of just putting it at the top of my post. I forgot how to do that though....heh.
use a software or hardware mod, i think the software mod gives you better results and is more easy. http://www.maxdownloads.com/~ian/wizzard/
If you want to get some good OCing results you also need some proper cooling. Use RivaTuner from Guru3d.com, and increase the core and mem clocks in small steps.
Try using PowerStrip. Its one powerful piece of software that allows you to do almost anything with your video card. http://www.entechtaiwan.com/ps.htm