I recently installed a graphics card.....(help)?

and all works fine, great graphics, i basicly installed a agp 8x into a 4x pc, and so far so gd no problems what so ever, part from the fan on the gcard, is making a very loud noise, like a buzzing sound, i did get a cable in the box which hooks the gcard up to the power supply and hard drive, but i never used that, should i? if not what is the cause of the sound