Fantom 1TB external USB drive failure, only half... Fantom Drives / G-Force MegaDisk / 1TB /

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Fantom Drives / G-Force MegaDisk / 1TB / 7200 / 16MB / USB 2.0 / External Hard Drive (MDU1000) The drive had been making a clicking sound (I didn't know that wasn't normal) for about 6 months. Suddenly, I started having files that could not be read and Mac Disk Utility says only 465Gb is available. I think this is a 2x500Gb drive and one of the drives has failed. I need a fix that's not going to bankrupt me.