I would guess that the 6600 has a lower clock than the GT and possibly less pipelines, check out the 2 other overclock threads for tools and links, they're all the same !! Let me know if you need any advice, having done it with my 6800GT I know what to do !
Those are 3 different OC'ing options based on whats going on..
Standard 2D - This is normal PC use, I wouldnt bother changing the clock speeds here.
Low Power 3D - This is for the less complex 3D, usually game menu systems etc.. You could overclock this, but its not needed.
Performance 3D - This is what you want to OC! You should slowly increase this value (5Mhz) and test it during a game.
Signature/Avatar nuking: none (can be changed in your profile)
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum
!! Let me know if you need any advice, having done it with my 6800GT I know what to do 
