I wanted to create a Windows 7 installation on a USB drive for my iMac, so I followed these instructions. Basically, they allow you to create a bootable USB drive with Windows installed on it without resolving to using boot camp. The internal drive on the iMac is not big enough to also hold a boot camp installation.

After creating the USB drive, I plugged it into my iMac, and opened the boot menu by holding the option-key during boot. But the USB drive was not shown as a boot option, only the internal hard disk.

But then I plugged the USB drive into a MacBook Pro, and this does display the USB disk as a bootable device.

Why doesn't my iMac show the USB drive as a boot option, when the MacBook does, and can I fix it?

My iMac specs are:

  • Retina 5K, 27-inch, Late 2015
  • 4GHz Intel Core i7
  • 16GB RAM
  • AMD Radeon R9 M395X 4096 MB
  • Running macOS 10.12.2

The MacBook specs are:

  • Retina, 15-inch, Early 2013
  • 2,7 GHz Intel Core i7
  • 16GB RAM
  • Intel HD Graphics 4000 1536MB
  • Running macOS 10.11.2

The USB is a 500GB USB3 Hard Disk (not SSD). The partitioning was done using a Windows 7 installation in running under VMWare Fusion 7.1.3 (on my MacBook).

Note I realized though, that I might not get this to work with Windows 7, as Windows 7 doesn't have USB3 support out of the box. Actually booting the USB on my MacBook results in a Blue Screen of Death. I might need to try Windows 10, but I don't have a source DVD or image.

  • We need more info. What versions of macOS are you running on each machine? Also, how did you create the bootable USB (i.e. with emulation software on a Mac, or with a PC)? If you used emulation software, which one and version? Finally, what are the exact specs of your 5K iMac? – Monomeeth Dec 31 '16 at 5:20
  • I know that at some point recently, Apple discontinued support for Windows 7 Mac drivers (it doesn't work on the newest hardware or boot camp software). Could it be that Apple never made Windows drivers for the iMac hardware? – NoahL Dec 31 '16 at 21:55

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