If you just want quiet regardless of performance then get a 4200RPM hdd. Otherwise the next one up is the 5400 RPM and finally the 7200 RPM. Obviously the higher ther RPM the better is the performance but at the price of quietness. Most of the time 5400 RPM is a good compromise. Since it is only loud during startup and mostly quiet during normal operation. Hitachi and samsung make good ones.