They have "hush kits" that consist of foam gaskets to isolate fan vibrations from the surrounding cabinetry.
Okay...if this doesn't get it, I'll look into the hush kits. I got the "quiet case" that helped some, but that cpu fan still sounds like a hairdryer. So while I was getting a new fan, I might as well get a better heatsink. And since I was going to get the fan and heatsink anyway, I might as well get some more memory...