Here is the exact info they have about that:
Here is a way to bypass the incompatibilities that the latest Detonator series drivers have with the Cool Bits registry hack. After installing drivers that do not allow video card over clocking by the Cool Bits hack.
1. Make sure the Display Properties window is CLOSED.
2. Insert the nVCpl.dll from an older set of detonator drivers ( I use the 6.49's) into C:\WINDOWS\SYSTEM, and click YES when asked to over write the current file.
3. Use the Cool Bits hack like normal, reboot, click Enable Clock Frequency Adjustments in [H]ardware Options, reboot again.
4. Tweak to your heart's content.
5. Lather rinse and repeat.