hi i have a macbook pro late 2009 15inch . the hd clicks!. it always does on turn on and when shutting down restarting. Other times it just does it randomly while surfing or idle. it is sSMART verified and verified on disk utility . it just did it ! getting pretty annoying lol . bought second hand but has never frozen or had flashing ? on start up. whats wrong with it should i be worried? thankss.