Hello- I'm having an issue that appears to be common, but what the hey, I'll throw in my two cents. About two weeks ago, I bought a Mac Mini (i5) and a Thunderbolt display to replace an aging iMac. I have a lot of audio files and decided to buy an external drive to use with iTunes. I bought a WD 3TB My Book and also have a Toshiba Canvio USB 3.0 drive. Using the Mini's USB ports, I get the drives on the desktop, but neither will mount. Same for a WD Passport USB 2.0 drive! I can add files to all the drives on the desktop, but cannot designate any of them as the destination for iTunes stuff. When I initially set up the Mini, I had a Time Machine backup on the Toshiba. It performed the transfer without a problem. Once the Mini was set up, however, the Canvio could not successfully perform another Time Machine backup. Said from returning the My Book drive and buying a Firewire device, I don't know what to do. Any solutions?