Hmmm I seem to remember having the same problem with my original desktop computer several years ago.
CAUSE: Bad HDD; heads would slam against the outer casing
SOLUTION: Replace HDD IMMEDIATELY and backup all data before you can't get to it anymore.
Mine started having that problem only 3 months after we got it and would only happen once in a while. But it progressively got worse unit 9 months latter is was happening all the time. Fortunately the drive was still under warranty.
Replace that sucker ASAP!!!! Buy a new HDD if necessary but dont let it keep "pinging" away; it will fail eventually.