I used the Sierra patch tool to make a bootable SD card (which is then inserted into a USB card reader). I've used this hardware setup before to install Yosemite with no issues. Anyway, using the Sierra patch with the current installer from the App Store, my 2008 imac will not recognize the SD card as a bootable disk. However, when I boot into the previous OS I can set the SD card as the boot medium. When I do this and restart, it begins to load the installer, but freezes at the end. I've had no issues with the machine prior to this. Any suggestions?