what make of drive is it and is it S.M.A.R.T. enabled?
when the computer starts up and if S.M.A.R.T.is turned on then,on the post screen you may notice the status of the drive here,should say healthy if all is well.
run a disk check start/my computer/right click the drive/properties/tools/error checking and tick both boxes and restart the computer(go make a cup of tea will take a while)
also try aida32 personal etd click here click storage/smart and look at the status here.
it may just be a noisy drive or the acoustic damping may not be enabled.hitachi feature tool will work with all drive makes and allow you to enable or disable it click here (half way down page)
my drive is whisper quiet when enabled and still not that audiable when disabled though.