I know this is Off Topic but maybe someone has 
  had a similar experience or can offer advice from their 
  expertise.
   
  I am going along, and all 
  of a sudden my main hard drive (C:) starts up an incessant and continuing 
  chatter.  Loud enough to really notice.
  There is no other 
  indication anything is wrong.  CPU cycles are normal for what is open. 
  (Usually have various programs with browser open with many tabs).  I have 
  extra RAM and an onboard monitor does not indicate that the RAM is low.  
  I defrag automatically every night.  I have latest download/OS 
  upgrades.
   
  I shut down all 
  applications and exit in normal manner (once I held the computer power on 
  button down to shut down without going through the shut down sequence--just to 
  try it that way).  Either method of shutdown makes the computer ..... well 
  .... shut down.  Then normal restart, and back to 
  business.
   
  These events occur every 
  so many days even a week or more. It has happened three or four times, and 
  does not seem to be increasing in frequency.
   
  Normally, this would call 
  for a new hard drive, but I have no clue as to cause and no indication that 
  the drive is getting ready to fail (like increased 
events).
   
  Any comments or 
  suggestions?
   
  Thanks,
  Ken
   
  I am backed up with full 
  image of drive on external drive so I am safe 
  from that standpoint.