Overclocking with RivaTuner

[Cook1]

I was able to open my card to 16 pipelines with Riva Tuner without a single hitch, can play all games and it's great. Now, how do I OC with it? Took a screenie to show what I mean

http://www.geocities.com/cook_295/untitled.JPG

See, I can't check the box that would enable me to low-level hardware OC.

Missing something?