If it sounds like an intermittent clicking, then you have a problem. If it's a consistent high speed clicking, it's the normal sound from the needle on the platter.
Could you pls clarify ? By "intermittent", do you mean during an actual I/O operation, whether it is intermittent ? the way I make it, the disk revs up, makes the loudish noise consistently and then dies back down once the operation is complete - don't know whether this description makes any sense but wanted to check on what you meant - thanks