If you're using ntune/nvidia ctrl panel to adjust, it's a bit flakey.
For me it always takes 2x or more tries, the 1st attempt does nothing and the second or third usually takes it up to 99%.
My temps are ~55c idle, ~64c max when the fan is max speed.my specs
opty175 & Scythe SCNJ-1100P
EVGA 133-K8-NF41 & G.Skill F1-3200PHU2-2GBZX (2x1GB 2-3-2-5) EVGA 8800gts 320mb
3 x hdd's & 1 x dvdold Gateway 500mhz server case
& 2 x 120mm fans & aerocool gatewatch
Antec TPII-480 blue