I`ve recently bought a GeForce 3 (Gainward Golden Sample) and put Detonator 4 on my system (Win ME). I downloaded GeTune and used the tweak on that to enable the overclocking function.
It worked fine for me until I tried tweaking around some more with GeTune then things went pear shaped.
So, I`d download it and just activate coolbits tweak, nothing else. Tweak from the Display properties tab...
Hope it helps