I'm using a mid 2012 Macbook Pro running Yosemite 10.10.5. I have a Windows 7 Ultimate iso and have run Boot Camp Assistant to 1)successfully create a Windows 7 install disk on a 32GB usb disk. 2)successfully download the Windows support software from Apple 3)set up the partition so that Windows 7 received 100GB (I know this is overkill, but for now, whatever) and press "install." The software begins to partition my drive accordingly. It is at this point that the same thing every single time happens: the computer reboots, a blank light gray screen comes on, is replaced with a blank black screen, then the the fans run like crazy, and...nothing. This seems to go on forever. Just a black screen with the fans running at max. I reboot again and one of several things happens, though I can't tell what I'm doing differently to get the different responses. 1)I reboot pushing the option key. a) I either see only my "Macintosh HD" profile. This takes me to my normal desktop. b) Sometimes another option is available (can't remember the name). This takes me to a frozen, distorted Windows icon. 2) I reboot without pushing the option key, bringing me to a black screen with the message: "No bootable device -- insert boot disk and press any key." Disk Utility is currently showing two partitions: Macintosh HD (900GB) and Bootcamp (99GB). The usb card shows that it has been formatted to be MS-DOS (FAT). I have also tried independently downloading and using Boot Camp 4 and Boot Camp 5.1, with no different results. Help?