This must be the question asked most. - If you like absolute silence: Any 2.5 drive using an 2.5 => 3.5 adapter. A SSD will do too obviously but is an overkill. - Any low speed version HDD. Cheaper is better in most cases. Performance will be identical and less energy => less heat => less fan noise! - The cheapest is buying an External USB drive and taking out the build-in HDD from that one. That is what I usually do myself.