External HD will boot fine with Macbook Air, but not with iMac

Discussion in 'iMac' started by thepiks, Jan 18, 2013.

  1. thepiks macrumors newbie

    Dec 17, 2012
    I have a BlacX duet in which I've cloned my old HD. I'm testing everything before I install it internally in my new iMac. IT books find via holding down option while usb'd to my Macbook Ait. However, as soon as I hook it up to my iMac USB, it has a circle with a slash through it after I select it as the boot disk. Any Ideas?
  2. MisterKeeks macrumors 68000


    Nov 15, 2012

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