check the bios system health warnings. if there enabled then disable them 1 at a time taking note of which your removing. if the noise stops then thats the part thats failing. it may just be the case open warning is being triggered. (hope its that, because if its not it means your either over heating, power fail or fan is failing.) if it continues to beep after everythin is disabled then look up the bios beep code for your bios manufacturer (displayed on the first splash screen at boot time)