My 2012 27" Mac keeps on hanging. It's got a 1TB SATA drive that I'm beginning to think is the problem. I've wiped the drive and reinstalled Snow Leopard and it started hanging pretty much straight away. Opening System preferences, opening folders, browsing the net etc pretty much anything causes the little colourful ball to start spinning around. I then installed OS/X on an external drive and although a bit slow it didn't hang. So I'm guessing it's the internal drive? Anything else I can try or any tests I can run to confirm the hard disk is cactus? Thanks