Hi I'm a final year student with ALL of my dissertation documents saved on to my external hard drive. I figured I should probably back these things up to dropbox and low and behold, when I plugged in my External Hard Drive, my mac doesn't seem to register it. You can't write this stuff! I'm using a 2010 macbook pro with OS X 10.8.2. with a 2.4 GHz processor. The hard drive is a Sonnics 250gb external hard drive with 2 usb plugs. When I plug the hard drive in, it is spinning and making al the usual noises - the red light is showing as it normally would, but it's not appearing on the desktop and doesn't seem to be in devices either. Please help!! ` (also apologies if this is in the wrong forum) Sarah.