I have exactly the same issue on my brand new Toshiba Satellite. I took it back straight away and got another brand new machine...... exact same noise, could both be bad HDD but the odds...... I would love to know if anyone has a different idea, sounds like click of death to me, but like I said, the odds for 2 machines in a row.
I audited my HDD with seatools on all scans, no probs found