That two-tone siren may be the one generated by the hardware-based OTP circuit, which you can't disable without modifying the board.
Are you overclocking at all at this point? If you are, you should go back to bog standard timings. If you aren't, or you continue having problems, I would investigate and make sure that the
HSF is properly seated on the CPU and that you have a very thin film of heat sink compound covering the entire surface of the chip.