My beloved quad-core i7 2012 mini was damaged last week in a freak anomalous electrical surge from a dubious firewire cable, which may have accumulated static or perhaps not been properly shielded from a cable wire it was touching. The firewire port made a loud pop when I plugged it into the Mac, and then I immediately smelled burning circuit board. The firewire soundboard at the other end of the cable was not turned on, and the power strip it was connected to was shut off. I dont understand how this could have happened. However the Mac is not totally dead, but now it only will run Windows. My El Capitan partition will not finsih booting El Capitan recovery partition will not finish booting Mountain Lion, El Capitan, and Sierra USB system installer flash drives will not finish booting - but the USB ports are still working. So any Mac OS partition, the progress bar is painfully slow, and if it ever gets to the end, the mac just sits there and the OS never mounts. BUT, Windows 7 boots and runs just fine, as if nothing is wrong. Windows device manager shows that my firewire controller and Bluetooth controller are non-functional. So, my theory is that MacOS refuses to finish booting because it can detect that there is hardware damage, whereas Windows just does not care. Has anyone ever heard of such a thing? A Mac that will only boot to Windows? I've no longer got a Macintosh, I've got an Apple PC. I could live without firewire and bluetooth, but I can't live with a Mac that wont run MacOS!