Hello, I have a Mac Pro that I bought in March of 2008 (refurbished form Apple). Last week I bought a new internal hard drive for it (Western Digital Caviar Black 1 TB Hard Drive SATA3G / 7200 / 32 MB. (My original hard drive is 250GB SATAT 3G / 7200 rpm / 8 MB.) I installed it in bay 2 and successfully formatted it. Ever since it has been in the computer, I hear loud buzzing sounds coming from it. They grow louder and then die away (it takes about 5 seconds for this cycle to happen). This cycle then repeats itself about every 30 seconds. Sometimes the buzzing cycles will get quieter and quieter until they stop all together, and then will start back up again. There seems to be no rhyme or reason as to why this happens. Does anyone know what may be going on or if this is a defective drive and I should return it? Any help is greatly appreciated!!! Thank you so much!