What GPU Overclocking utility are Vista users supposed to use?

I have Vista 64 and Rivatuner will not work, Ati tool specifically states it will only work on up to XP.

Rivatuner on startup:

"Driver signing enforcement must be disabled in order to start riva tuner under vista x64. Do you want to disable driver signing enforcement right now and reboot the system to apply the changes?"

I Hit yes but it still pops up ever time I start it. Now I click no and it starts up but there are no driver level overclocking options.

Can anyone help me please?

Once I find a way to OC my GPU I would like to run performance comparasons with XP and Vista in crysis. I ran Crysis on all setting HIGH spec and got 2 more fps in Vista. I was very surprised and would now like to bench Overclocking results!