Check the Enable Graphics Overdrive box.
Use the sliders.
Mine are max on my 5850.
Select a fan speed.
Ati doesn't offer crazy overclocking functions.
It's all within safe limits.
Use a program like GPU-Z to monitor temps.http://www.techpowerup.com/downloads/2092/TechPowerUp_GPU-Z_v0.5.8.html
another question dear... i have recently played Battlefield 3 and COD MW3, and NFS the Run on my unclocked 5670 ddr5 1gb card..
All games runs smoothly without any problem on Max setting...so should i overclock it or keep it as it is working now... no game feel laggy or slow...i even posted my game play here http://youtu.be/1-0tkEk-Bx0
you can watch in 720p hd also
so what u say should i overclock it or overclock it when it get slower