My fans are noisy... but the one on my 6600GT drives me bloody mad. It sounds like a mini jet engine
I know the feeling. Check out www.quietpc.com ASAP.I have purchased a CPU fan, VGA cooler, and a Hard Drive silencer.
Result? .. Bliss. Recommended stuff.
For your 6600 GT (AGP) the VF700 cooler should do the trick but read the compatibility details first.