IMac :: My Systen Cannot Recognise Hard Drive?

I have a 24 inch iMac which was virtually silent. Last week the hard drive started failing so Apple replaced it under my AppleCare warranty. The trouble is now I constantly hear the new hard drive reading data, even when I?m listening to music I can hear the hard drive in the background which is very annoying. I never heard any noise from the original hard drive. I did notice that the replacement drive is a Seagate unit where the original drive was a WD. I called Apple again and they want me to bring it into the Apple Store again. I just don?t want to be going back and forth with this thing and not have anything improve. Shouldn?t I get it back from repair exactly the same as it originally was? I wonder if I they can specify what brand hard drive Apple sends to the store.