Hard drive on latest macbook pro 17 accessed too often
I have had great luck using the Activity Monitor to find out what's running on my Macs.  It should point you to the app that is accessing the hard drive.  I would start in "My Processes" and look to see which apps are consuming CPUs.  If this view does not help, then try switching to "All processes, Hierarchically" which will include your Apps and core System apps.  The bad guy should be consuming lots of CPUs.

You can also run the Apple hardware test that Apple included on your OS X disks.  This test is explain in Apple Support document HT1509.

Given your past experience with the Apple spinning beach ball, I think there's an app behind this but between Activity Monitor and Hardware test, you'll have a better idea of what's going on.