Download Ntune from Nvidia. After you do this, enter nTune and go to GPU Performance. On the cooling area, click on manual fan control. Slide the slider all the way to the right and click on APPLY. You might have to do this a couple of times for some reason for the settings to stick. Your fan will be PERCEPTIBLY louder, but I have mine INSIDE an open-backed desk and I run my 8800gts at 600/900mhz and I only see maybe 60C full load with the fan on high. Now, if I open up my computer cabinet in the desk, it drops to 51C under full load with STOCK cooling.
Also, for some reason, it wont allow you to save your overclocks to start automatically, so you will have to do this everytime you boot, or figure it out with Ntune. I have no patience for that crap, so I just turn it up before playing.