My pc makes a high pitched beeping noise under heavy load

windows 7 Pro 64bit SP1(always updated durrrrr)
Corsair SSD Force Series 3, 120GB 2.5"
Western Digital® Desktop Black 1TB x1
Western Digital Caviar® Green? 2TB x3
Nvidia Geforce GTX 480(Zalman VF3000F GTX480 GPU-heatsink)
ASUS Xonar D2X/XDT, 7.1 channel
Corsair A70 CPU heatsink
ASUS M4A89GTD PRO/USB3
AMD phenom II X6 1055T processor 2.80GHz(activated the sixth core)
Corsair Vengeance DDR3 1600MHz 8GB CL8
Fractal design XL

this my build, this pc makes a high frequent beeping noise under heavy load, i noticed it when folding@home runs at 99.999%.